diff --git a/HISTORY.rst b/HISTORY.rst
index 04dfea3b8..9ba06fe46 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -48,6 +48,7 @@ End-User Summary
 - Fixing problem with ACMD classifiction where VUS-3 was given but should be LB-2 (#359)
 - Adding REST API for creating small variant queries (#332)
 - Fixing beaconsite queries with dots in the key id (#369)
+- Allowing joint queries of larger cohorts (#241)
 
 Full Change List
 ================
@@ -106,6 +107,8 @@ Full Change List
 - Adding REST API for creating small variant queries (#332)
 - Upgrading sodar-core dependency to 0.10.10
 - Fixing beaconsite queries with dots in the key id (#369)
+- Allowing joint queries of larger cohorts (#241).
+  This is achieved by performing fewer UNION queries (at most ``VARFISH_QUERY_MAX_UNION=20`` at one time).
 
 -------
 v0.23.9
diff --git a/config/settings/base.py b/config/settings/base.py
index d1db149be..c91193f39 100644
--- a/config/settings/base.py
+++ b/config/settings/base.py
@@ -502,6 +502,9 @@ def set_logging(level=None):
     "FIELD_ENCRYPTION_KEY", "_XRAzgLd6NHj8G4q9FNV0p3Um9g4hy8BPBN-AL0JWO0="
 )
 
+# Number of cases to perform in one query for joint queries.
+QUERY_MAX_UNION = env.int("VARFISH_QUERY_MAX_UNION", 20)
+
 # Varfish: Exomiser
 # ------------------------------------------------------------------------------
 
diff --git a/docs_manual/admin_config.rst b/docs_manual/admin_config.rst
index ab652b397..a5fd3f814 100644
--- a/docs_manual/admin_config.rst
+++ b/docs_manual/admin_config.rst
@@ -185,11 +185,14 @@ In the default ``docker-compose`` setup, postgres server is thus not exposed to
 Miscellaneous Configuration
 ---------------------------
 
-``VARFISH_LOGIN_PAGE_TEXT=``
+``VARFISH_LOGIN_PAGE_TEXT``
     Text to display on the login page.
 ``FIELD_ENCRYPTION_KEY``
     Key to use for encrypting secrets in the database (such as saved public keys for the Beacon Site feature).
     You can generate such a key with the following command: ``python -c 'import os, base64; print(base64.urlsafe_b64encode(os.urandom(32)))'``.
+``VARFISH_QUERY_MAX_UNION``
+    Maximal number of cases to query for at the same time for joint queries.
+    Default is ``20``.
 
 --------------------
 Sentry Configuration
diff --git a/variants/queries.py b/variants/queries.py
index 4855605bc..2ab9dd228 100644
--- a/variants/queries.py
+++ b/variants/queries.py
@@ -1,3 +1,4 @@
+import contextlib
 from itertools import chain
 import typing
 
@@ -1598,6 +1599,20 @@ def to_stmt(self, kwargs, order_by=None):
         return union(comphet_stmt, default_stmt).order_by(*(order_by or []))
 
 
+def _chunked(arr, max_size):
+    chunks = []
+    i = 0
+    while i < len(arr):
+        chunks.append(arr[i : i + max_size])
+        i += max_size
+    return chunks
+
+
+class _ClosingWrapper(list):
+    def closing(self):
+        pass
+
+
 class CasePrefetchQuery:
     builder = QueryPartsBuilder
 
@@ -1618,30 +1633,39 @@ def run(self, kwargs):
             column("alternative"),
             column("family_name"),
         ]
-        stmts = []
-        for case in self.cases:
-            comp_het_index = kwargs.get("compound_recessive_indices", {}).get(case.name)
-            recessive_index = kwargs.get("recessive_indices", {}).get(case.name)
-            if comp_het_index and self.query_id is None:
-                # Set the current compound recessive index
-                kwargs["compound_recessive_index"] = comp_het_index
-                combiner = CompHetCombiner(case, self.builder)
-            elif recessive_index and self.query_id is None:
-                # Set the current compound recessive index
-                kwargs["compound_recessive_index"] = recessive_index
-                combiner = RecessiveCombiner(case, self.builder)
-            else:  # compound recessive not in kwargs or disabled
-                combiner = DefaultCombiner(case, self.builder, self.query_id)
-            stmts.append(combiner.to_stmt(kwargs))
-        stmt = union(*stmts).order_by(*order_by)
-        if settings.DEBUG:
-            print(
-                "\n"
-                + sqlparse.format(
-                    stmt.compile(self.engine).string, reindent=True, keyword_case="upper"
+        result = []
+        chunks = _chunked(self.cases, settings.QUERY_MAX_UNION)
+        for chunk in chunks:
+            stmts = []
+            for case in chunk:
+                comp_het_index = kwargs.get("compound_recessive_indices", {}).get(case.name)
+                recessive_index = kwargs.get("recessive_indices", {}).get(case.name)
+                if comp_het_index and self.query_id is None:
+                    # Set the current compound recessive index
+                    kwargs["compound_recessive_index"] = comp_het_index
+                    combiner = CompHetCombiner(case, self.builder)
+                elif recessive_index and self.query_id is None:
+                    # Set the current compound recessive index
+                    kwargs["compound_recessive_index"] = recessive_index
+                    combiner = RecessiveCombiner(case, self.builder)
+                else:  # compound recessive not in kwargs or disabled
+                    combiner = DefaultCombiner(case, self.builder, self.query_id)
+                stmts.append(combiner.to_stmt(kwargs))
+            stmt = union(*stmts).order_by(*order_by)
+            if settings.DEBUG:
+                print(
+                    "\n"
+                    + sqlparse.format(
+                        stmt.compile(self.engine).string, reindent=True, keyword_case="upper"
+                    )
                 )
-            )
-        return self.engine.execute(stmt)
+            query_res = self.engine.execute(stmt)
+            if len(chunks) == 1:
+                return query_res
+            else:
+                with contextlib.closing(query_res) as query_res:
+                    result += list(query_res)
+        return _ClosingWrapper(result)
 
 
 class CaseLoadPrefetchedQuery(CasePrefetchQuery):