diff --git a/flang/include/flang/Evaluate/tools.h b/flang/include/flang/Evaluate/tools.h
index 8c872a0579c8e..29065c9f01ecf 100644
--- a/flang/include/flang/Evaluate/tools.h
+++ b/flang/include/flang/Evaluate/tools.h
@@ -19,6 +19,7 @@
 #include "flang/Evaluate/type.h"
 #include "flang/Parser/message.h"
 #include "flang/Semantics/attr.h"
+#include "flang/Semantics/scope.h"
 #include "flang/Semantics/symbol.h"
 #include <array>
 #include <optional>
@@ -1240,6 +1241,35 @@ inline bool HasCUDAAttrs(const Expr<SomeType> &expr) {
   return false;
 }
 
+/// Check if the expression is a mix of host and device variables that require
+/// implicit data transfer.
+inline bool HasCUDAImplicitTransfer(const Expr<SomeType> &expr) {
+  unsigned hostSymbols{0};
+  unsigned deviceSymbols{0};
+  for (const Symbol &sym : CollectSymbols(expr)) {
+    if (const auto *details =
+            sym.GetUltimate().detailsIf<semantics::ObjectEntityDetails>()) {
+      if (details->cudaDataAttr()) {
+        ++deviceSymbols;
+      } else {
+        if (sym.owner().IsDerivedType()) {
+          if (const auto *details =
+                  sym.owner()
+                      .GetSymbol()
+                      ->GetUltimate()
+                      .detailsIf<semantics::ObjectEntityDetails>()) {
+            if (details->cudaDataAttr()) {
+              ++deviceSymbols;
+            }
+          }
+        }
+        ++hostSymbols;
+      }
+    }
+  }
+  return hostSymbols > 0 && deviceSymbols > 0;
+}
+
 } // namespace Fortran::evaluate
 
 namespace Fortran::semantics {
diff --git a/flang/lib/Lower/Bridge.cpp b/flang/lib/Lower/Bridge.cpp
index 5bba0978617c7..478c8f4c17ec4 100644
--- a/flang/lib/Lower/Bridge.cpp
+++ b/flang/lib/Lower/Bridge.cpp
@@ -3710,16 +3710,18 @@ class FirConverter : public Fortran::lower::AbstractConverter {
     return false;
   }
 
-  static void genCUDADataTransfer(fir::FirOpBuilder &builder,
-                                  mlir::Location loc, bool lhsIsDevice,
-                                  hlfir::Entity &lhs, bool rhsIsDevice,
-                                  hlfir::Entity &rhs) {
+  void genCUDADataTransfer(fir::FirOpBuilder &builder, mlir::Location loc,
+                           const Fortran::evaluate::Assignment &assign,
+                           hlfir::Entity &lhs, hlfir::Entity &rhs) {
+    bool lhsIsDevice = Fortran::evaluate::HasCUDAAttrs(assign.lhs);
+    bool rhsIsDevice = Fortran::evaluate::HasCUDAAttrs(assign.rhs);
     if (rhs.isBoxAddressOrValue() || lhs.isBoxAddressOrValue())
       TODO(loc, "CUDA data transfler with descriptors");
+
+    // device = host
     if (lhsIsDevice && !rhsIsDevice) {
       auto transferKindAttr = fir::CUDADataTransferKindAttr::get(
           builder.getContext(), fir::CUDADataTransferKind::HostDevice);
-      // device = host
       if (!rhs.isVariable()) {
         auto associate = hlfir::genAssociateExpr(
             loc, builder, rhs, rhs.getType(), ".cuf_host_tmp");
@@ -3732,7 +3734,73 @@ class FirConverter : public Fortran::lower::AbstractConverter {
       }
       return;
     }
-    TODO(loc, "Assignement with CUDA Fortran variables");
+
+    // host = device
+    if (!lhsIsDevice && rhsIsDevice) {
+      auto transferKindAttr = fir::CUDADataTransferKindAttr::get(
+          builder.getContext(), fir::CUDADataTransferKind::DeviceHost);
+      if (!rhs.isVariable()) {
+        // evaluateRhs loads scalar. Look for the memory reference to be used in
+        // the transfer.
+        if (mlir::isa_and_nonnull<fir::LoadOp>(rhs.getDefiningOp())) {
+          auto loadOp = mlir::dyn_cast<fir::LoadOp>(rhs.getDefiningOp());
+          builder.create<fir::CUDADataTransferOp>(loc, loadOp.getMemref(), lhs,
+                                                  transferKindAttr);
+          return;
+        }
+      } else {
+        builder.create<fir::CUDADataTransferOp>(loc, rhs, lhs,
+                                                transferKindAttr);
+      }
+      return;
+    }
+
+    if (lhsIsDevice && rhsIsDevice) {
+      assert(rhs.isVariable() && "CUDA Fortran assignment rhs is not legal");
+      auto transferKindAttr = fir::CUDADataTransferKindAttr::get(
+          builder.getContext(), fir::CUDADataTransferKind::DeviceDevice);
+      builder.create<fir::CUDADataTransferOp>(loc, rhs, lhs, transferKindAttr);
+      return;
+    }
+    llvm_unreachable("Unhandled CUDA data transfer");
+  }
+
+  llvm::SmallVector<mlir::Value>
+  genCUDAImplicitDataTransfer(fir::FirOpBuilder &builder, mlir::Location loc,
+                              const Fortran::evaluate::Assignment &assign) {
+    llvm::SmallVector<mlir::Value> temps;
+    localSymbols.pushScope();
+    auto transferKindAttr = fir::CUDADataTransferKindAttr::get(
+        builder.getContext(), fir::CUDADataTransferKind::DeviceHost);
+    unsigned nbDeviceResidentObject = 0;
+    for (const Fortran::semantics::Symbol &sym :
+         Fortran::evaluate::CollectSymbols(assign.rhs)) {
+      if (const auto *details =
+              sym.GetUltimate()
+                  .detailsIf<Fortran::semantics::ObjectEntityDetails>()) {
+        if (details->cudaDataAttr()) {
+          if (sym.owner().IsDerivedType() && IsAllocatable(sym.GetUltimate()))
+            TODO(loc, "Device resident allocatable derived-type component");
+          // TODO: This should probably being checked in semantic and give a
+          // proper error.
+          assert(
+              nbDeviceResidentObject <= 1 &&
+              "Only one reference to the device resident object is supported");
+          auto addr = getSymbolAddress(sym);
+          hlfir::Entity entity{addr};
+          auto [temp, cleanup] =
+              hlfir::createTempFromMold(loc, builder, entity);
+          auto needCleanup = fir::getIntIfConstant(cleanup);
+          if (needCleanup && *needCleanup)
+            temps.push_back(temp);
+          addSymbol(sym, temp, /*forced=*/true);
+          builder.create<fir::CUDADataTransferOp>(loc, addr, temp,
+                                                  transferKindAttr);
+          ++nbDeviceResidentObject;
+        }
+      }
+    }
+    return temps;
   }
 
   void genDataAssignment(
@@ -3741,8 +3809,13 @@ class FirConverter : public Fortran::lower::AbstractConverter {
     mlir::Location loc = getCurrentLocation();
     fir::FirOpBuilder &builder = getFirOpBuilder();
 
-    bool lhsIsDevice = Fortran::evaluate::HasCUDAAttrs(assign.lhs);
-    bool rhsIsDevice = Fortran::evaluate::HasCUDAAttrs(assign.rhs);
+    bool isCUDATransfer = Fortran::evaluate::HasCUDAAttrs(assign.lhs) ||
+                          Fortran::evaluate::HasCUDAAttrs(assign.rhs);
+    bool hasCUDAImplicitTransfer =
+        Fortran::evaluate::HasCUDAImplicitTransfer(assign.rhs);
+    llvm::SmallVector<mlir::Value> implicitTemps;
+    if (hasCUDAImplicitTransfer)
+      implicitTemps = genCUDAImplicitDataTransfer(builder, loc, assign);
 
     // Gather some information about the assignment that will impact how it is
     // lowered.
@@ -3800,12 +3873,16 @@ class FirConverter : public Fortran::lower::AbstractConverter {
       Fortran::lower::StatementContext localStmtCtx;
       hlfir::Entity rhs = evaluateRhs(localStmtCtx);
       hlfir::Entity lhs = evaluateLhs(localStmtCtx);
-      if (lhsIsDevice || rhsIsDevice) {
-        genCUDADataTransfer(builder, loc, lhsIsDevice, lhs, rhsIsDevice, rhs);
-      } else {
+      if (isCUDATransfer && !hasCUDAImplicitTransfer)
+        genCUDADataTransfer(builder, loc, assign, lhs, rhs);
+      else
         builder.create<hlfir::AssignOp>(loc, rhs, lhs,
                                         isWholeAllocatableAssignment,
                                         keepLhsLengthInAllocatableAssignment);
+      if (hasCUDAImplicitTransfer) {
+        localSymbols.popScope();
+        for (mlir::Value temp : implicitTemps)
+          builder.create<fir::FreeMemOp>(loc, temp);
       }
       return;
     }
diff --git a/flang/test/Lower/CUDA/cuda-data-transfer.cuf b/flang/test/Lower/CUDA/cuda-data-transfer.cuf
index 54226b8623e6a..4ebd736315bcb 100644
--- a/flang/test/Lower/CUDA/cuda-data-transfer.cuf
+++ b/flang/test/Lower/CUDA/cuda-data-transfer.cuf
@@ -2,6 +2,12 @@
 
 ! Test CUDA Fortran data transfer using assignment statements.
 
+module mod1
+  type :: t1
+    integer :: i
+  end type
+end
+
 subroutine sub1()
   integer, device :: m
   integer, device :: adev(10)
@@ -55,3 +61,61 @@ end
 ! CHECK: %[[ASSOC:.*]]:3 = hlfir.associate %[[ELEMENTAL]](%{{.*}}) {uniq_name = ".cuf_host_tmp"} : (!hlfir.expr<10xi32>, !fir.shape<1>) -> (!fir.ref<!fir.array<10xi32>>, !fir.ref<!fir.array<10xi32>>, i1)
 ! CHECK: fir.cuda_data_transfer %[[ASSOC]]#0 to %[[ADEV]]#0 {transfer_kind = #fir.cuda_transfer<host_device>} : !fir.ref<!fir.array<10xi32>>, !fir.ref<!fir.array<10xi32>>
 ! CHECK: hlfir.end_associate %[[ASSOC]]#1, %[[ASSOC]]#2 : !fir.ref<!fir.array<10xi32>>, i1
+
+subroutine sub2()
+  integer, device :: m
+  integer, device :: adev(10), bdev(10)
+  integer :: i, ahost(10), bhost(10)
+
+  ahost = adev
+
+  i = m
+
+  ahost(1:5) = adev(1:5)
+
+  bdev = adev
+
+  ! Implicit data transfer of adev before evaluation.
+  bhost = ahost + adev
+
+end
+
+! CHECK-LABEL: func.func @_QPsub2()
+! CHECK: %[[ADEV:.*]]:2 = hlfir.declare %{{.*}}(%{{.*}}) {cuda_attr = #fir.cuda<device>, uniq_name = "_QFsub2Eadev"} : (!fir.ref<!fir.array<10xi32>>, !fir.shape<1>) -> (!fir.ref<!fir.array<10xi32>>, !fir.ref<!fir.array<10xi32>>)
+! CHECK: %[[AHOST:.*]]:2 = hlfir.declare %{{.*}}(%{{.*}}) {uniq_name = "_QFsub2Eahost"} : (!fir.ref<!fir.array<10xi32>>, !fir.shape<1>) -> (!fir.ref<!fir.array<10xi32>>, !fir.ref<!fir.array<10xi32>>)
+! CHECK: %[[BDEV:.*]]:2 = hlfir.declare %{{.*}}(%{{.*}}) {cuda_attr = #fir.cuda<device>, uniq_name = "_QFsub2Ebdev"} : (!fir.ref<!fir.array<10xi32>>, !fir.shape<1>) -> (!fir.ref<!fir.array<10xi32>>, !fir.ref<!fir.array<10xi32>>)
+! CHECK: %[[BHOST:.*]]:2 = hlfir.declare %{{.*}}(%{{.*}}) {uniq_name = "_QFsub2Ebhost"} : (!fir.ref<!fir.array<10xi32>>, !fir.shape<1>) -> (!fir.ref<!fir.array<10xi32>>, !fir.ref<!fir.array<10xi32>>)
+! CHECK: %[[I:.*]]:2 = hlfir.declare %{{.*}} {uniq_name = "_QFsub2Ei"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+! CHECK: %[[M:.*]]:2 = hlfir.declare %{{.*}} {cuda_attr = #fir.cuda<device>, uniq_name = "_QFsub2Em"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+! CHECK: fir.cuda_data_transfer %[[ADEV]]#0 to %[[AHOST]]#0 {transfer_kind = #fir.cuda_transfer<device_host>} : !fir.ref<!fir.array<10xi32>>, !fir.ref<!fir.array<10xi32>>
+! CHECK: fir.cuda_data_transfer %[[M]]#0 to %[[I]]#0 {transfer_kind = #fir.cuda_transfer<device_host>} : !fir.ref<i32>, !fir.ref<i32>
+
+! CHECK: %[[DES_ADEV:.*]] = hlfir.designate %[[ADEV]]#0 (%{{.*}}:%{{.*}}:%{{.*}})  shape %{{.*}} : (!fir.ref<!fir.array<10xi32>>, index, index, index, !fir.shape<1>) -> !fir.ref<!fir.array<5xi32>>
+! CHECK: %[[DES_AHOST:.*]] = hlfir.designate %[[AHOST]]#0 (%{{.*}}:%{{.*}}:%{{.*}})  shape %{{.*}} : (!fir.ref<!fir.array<10xi32>>, index, index, index, !fir.shape<1>) -> !fir.ref<!fir.array<5xi32>>
+! CHECK: fir.cuda_data_transfer %[[DES_ADEV]] to %[[DES_AHOST]] {transfer_kind = #fir.cuda_transfer<device_host>} : !fir.ref<!fir.array<5xi32>>, !fir.ref<!fir.array<5xi32>>
+
+! CHECK: fir.cuda_data_transfer %[[ADEV]]#0 to %[[BDEV]]#0 {transfer_kind = #fir.cuda_transfer<device_device>} : !fir.ref<!fir.array<10xi32>>, !fir.ref<!fir.array<10xi32>>
+
+! CHECK: %[[TEMP:.*]] = fir.allocmem !fir.array<10xi32> {bindc_name = ".tmp", uniq_name = ""}
+! CHECK: %[[DECL_TEMP:.*]]:2 = hlfir.declare %[[TEMP]](%{{.*}}) {uniq_name = ".tmp"} : (!fir.heap<!fir.array<10xi32>>, !fir.shape<1>) -> (!fir.heap<!fir.array<10xi32>>, !fir.heap<!fir.array<10xi32>>)
+! CHECK: %[[ADEV_TEMP:.*]]:2 = hlfir.declare %21#0 {cuda_attr = #fir.cuda<device>, uniq_name = "_QFsub2Eadev"} : (!fir.heap<!fir.array<10xi32>>) -> (!fir.heap<!fir.array<10xi32>>, !fir.heap<!fir.array<10xi32>>)
+! CHECK: fir.cuda_data_transfer %[[ADEV]]#1 to %[[DECL_TEMP]]#0 {transfer_kind = #fir.cuda_transfer<device_host>} : !fir.ref<!fir.array<10xi32>>, !fir.heap<!fir.array<10xi32>>
+! CHECK: %[[ELEMENTAL:.*]] = hlfir.elemental %{{.*}} unordered : (!fir.shape<1>) -> !hlfir.expr<10xi32>
+! CHECK: hlfir.assign %[[ELEMENTAL]] to %[[BHOST]]#0 : !hlfir.expr<10xi32>, !fir.ref<!fir.array<10xi32>>
+! CHECK: fir.freemem %[[DECL_TEMP]]#0 : !fir.heap<!fir.array<10xi32>>
+
+subroutine sub3()
+  use mod1
+  type(t1), device :: t
+  integer :: ahost(10), bhost(10)
+
+  bhost = ahost + t%i
+end
+
+! CHECK-LABEL: func.func @_QPsub3()
+! CHECK: %[[TMP:.*]] = fir.alloca !fir.type<_QMmod1Tt1{i:i32}> {bindc_name = ".tmp"}
+! CHECK: %[[AHOST:.*]]:2 = hlfir.declare %{{.*}}(%{{.*}}) {uniq_name = "_QFsub3Eahost"} : (!fir.ref<!fir.array<10xi32>>, !fir.shape<1>) -> (!fir.ref<!fir.array<10xi32>>, !fir.ref<!fir.array<10xi32>>)
+! CHECK: %[[BHOST:.*]]:2 = hlfir.declare %{{.*}}(%{{.*}}) {uniq_name = "_QFsub3Ebhost"} : (!fir.ref<!fir.array<10xi32>>, !fir.shape<1>) -> (!fir.ref<!fir.array<10xi32>>, !fir.ref<!fir.array<10xi32>>)
+! CHECK: %[[T:.*]]:2 = hlfir.declare %7 {cuda_attr = #fir.cuda<device>, uniq_name = "_QFsub3Et"} : (!fir.ref<!fir.type<_QMmod1Tt1{i:i32}>>) -> (!fir.ref<!fir.type<_QMmod1Tt1{i:i32}>>, !fir.ref<!fir.type<_QMmod1Tt1{i:i32}>>)
+! CHECK: %[[TMP_DECL:.*]]:2 = hlfir.declare %0 {uniq_name = ".tmp"} : (!fir.ref<!fir.type<_QMmod1Tt1{i:i32}>>) -> (!fir.ref<!fir.type<_QMmod1Tt1{i:i32}>>, !fir.ref<!fir.type<_QMmod1Tt1{i:i32}>>)
+! CHECK: fir.cuda_data_transfer %[[T]]#1 to %[[TMP_DECL]]#0 {transfer_kind = #fir.cuda_transfer<device_host>} : !fir.ref<!fir.type<_QMmod1Tt1{i:i32}>>, !fir.ref<!fir.type<_QMmod1Tt1{i:i32}>>