diff --git a/mat64/index_bound_checks.go b/mat64/index_bound_checks.go
index ff06c71..2e03752 100644
--- a/mat64/index_bound_checks.go
+++ b/mat64/index_bound_checks.go
@@ -8,6 +8,8 @@
 
 package mat64
 
+import "github.com/gonum/blas"
+
 func (m *Dense) At(r, c int) float64 {
 	return m.at(r, c)
 }
@@ -63,3 +65,49 @@ func (m *Vector) set(r int, v float64) {
 	}
 	m.mat.Data[r*m.mat.Inc] = v
 }
+
+// At returns the element at row r and column c.
+func (t *Triangular) At(r, c int) float64 {
+	return t.at(r, c)
+}
+
+func (t *Triangular) at(r, c int) float64 {
+	if r >= t.mat.N || r < 0 {
+		panic(ErrRowAccess)
+	}
+	if c >= t.mat.N || c < 0 {
+		panic(ErrColAccess)
+	}
+	if t.mat.Uplo == blas.Upper {
+		if r > c {
+			return 0
+		}
+		return t.mat.Data[r*t.mat.Stride+c]
+	}
+	if r < c {
+		return 0
+	}
+	return t.mat.Data[r*t.mat.Stride+c]
+}
+
+// Set sets the element at row r and column c. Set panics if the location is outside
+// the appropriate half of the matrix.
+func (t *Triangular) Set(r, c int, v float64) {
+	t.set(r, c, v)
+}
+
+func (t *Triangular) set(r, c int, v float64) {
+	if r >= t.mat.N || r < 0 {
+		panic(ErrRowAccess)
+	}
+	if c >= t.mat.N || c < 0 {
+		panic(ErrColAccess)
+	}
+	if t.mat.Uplo == blas.Upper && r > c {
+		panic("mat64: triangular set out of bounds")
+	}
+	if t.mat.Uplo == blas.Lower && r < c {
+		panic("mat64: triangular set out of bounds")
+	}
+	t.mat.Data[r*t.mat.Stride+c] = v
+}
diff --git a/mat64/index_no_bound_checks.go b/mat64/index_no_bound_checks.go
index 5ca231d..cbefbc6 100644
--- a/mat64/index_no_bound_checks.go
+++ b/mat64/index_no_bound_checks.go
@@ -8,6 +8,8 @@
 
 package mat64
 
+import "github.com/gonum/blas"
+
 func (m *Dense) At(r, c int) float64 {
 	if r >= m.mat.Rows || r < 0 {
 		panic(ErrRowAccess)
@@ -63,3 +65,49 @@ func (m *Vector) Set(r, c int, v float64) {
 func (m *Vector) set(r int, v float64) {
 	m.mat.Data[r*m.mat.Inc] = v
 }
+
+// At returns the element at row r and column c.
+func (t *Triangular) At(r, c int) float64 {
+	if r >= t.mat.N || r < 0 {
+		panic(ErrRowAccess)
+	}
+	if c >= t.mat.N || c < 0 {
+		panic(ErrColAccess)
+	}
+	return t.at(r, c)
+}
+
+func (t *Triangular) at(r, c int) float64 {
+	if t.mat.Uplo == blas.Upper {
+		if r > c {
+			return 0
+		}
+		return t.mat.Data[r*t.mat.Stride+c]
+	}
+	if r < c {
+		return 0
+	}
+	return t.mat.Data[r*t.mat.Stride+c]
+}
+
+// Set sets the element at row r and column c. Set panics if the location is outside
+// the appropriate half of the matrix.
+func (t *Triangular) Set(r, c int, v float64) {
+	if r >= t.mat.N || r < 0 {
+		panic(ErrRowAccess)
+	}
+	if c >= t.mat.N || c < 0 {
+		panic(ErrColAccess)
+	}
+	if t.mat.Uplo == blas.Upper && r > c {
+		panic("mat64: triangular set out of bounds")
+	}
+	if t.mat.Uplo == blas.Lower && r < c {
+		panic("mat64: triangular set out of bounds")
+	}
+	t.set(r, c, v)
+}
+
+func (t *Triangular) set(r, c int, v float64) {
+	t.mat.Data[r*t.mat.Stride+c] = v
+}
diff --git a/mat64/triangular.go b/mat64/triangular.go
new file mode 100644
index 0000000..e8d6888
--- /dev/null
+++ b/mat64/triangular.go
@@ -0,0 +1,55 @@
+package mat64
+
+import (
+	"github.com/gonum/blas"
+	"github.com/gonum/blas/blas64"
+)
+
+var (
+	triangular *Triangular
+
+	_ Matrix  = triangular
+	_ Mutable = triangular
+)
+
+// Triangular represents an upper or lower triangular matrix.
+type Triangular struct {
+	mat blas64.Triangular
+}
+
+// NewTriangular constructs an n x n triangular matrix. The constructed matrix
+// is upper triangular if upper == true, and lower triangular otherwise.
+// If len(mat) == n * n, mat will be used to hold the underlying data, or if
+// mat == nil, new data will be allocated.
+// The underlying data representation is the same as that of a Dense matrix,
+// except the values of the entries in the opposite half are completely ignored.
+func NewTriangular(n int, upper bool, mat []float64) *Triangular {
+	if n < 0 {
+		panic("mat64: negative dimension")
+	}
+	if mat != nil && n*n != len(mat) {
+		panic(ErrShape)
+	}
+	if mat == nil {
+		mat = make([]float64, n*n)
+	}
+	uplo := blas.Lower
+	if upper {
+		uplo = blas.Upper
+	}
+	return &Triangular{blas64.Triangular{
+		N:      n,
+		Stride: n,
+		Data:   mat,
+		Uplo:   uplo,
+		Diag:   blas.NonUnit,
+	}}
+}
+
+func (t *Triangular) Dims() (r, c int) {
+	return t.mat.N, t.mat.N
+}
+
+func (t *Triangular) RawTriangular() blas64.Triangular {
+	return t.mat
+}
diff --git a/mat64/triangular_test.go b/mat64/triangular_test.go
new file mode 100644
index 0000000..69ae862
--- /dev/null
+++ b/mat64/triangular_test.go
@@ -0,0 +1,76 @@
+package mat64
+
+import (
+	"github.com/gonum/blas"
+	"github.com/gonum/blas/blas64"
+	"gopkg.in/check.v1"
+)
+
+func (s *S) TestNewTriangular(c *check.C) {
+	for i, test := range []struct {
+		data  []float64
+		N     int
+		upper bool
+		mat   *Triangular
+	}{
+		{
+			data: []float64{
+				1, 2, 3,
+				4, 5, 6,
+				7, 8, 9,
+			},
+			N:     3,
+			upper: true,
+			mat: &Triangular{blas64.Triangular{
+				N:      3,
+				Stride: 3,
+				Uplo:   blas.Upper,
+				Data:   []float64{1, 2, 3, 4, 5, 6, 7, 8, 9},
+				Diag:   blas.NonUnit,
+			}},
+		},
+	} {
+		t := NewTriangular(test.N, test.upper, test.data)
+		rows, cols := t.Dims()
+		c.Check(rows, check.Equals, test.N, check.Commentf("Test %d", i))
+		c.Check(cols, check.Equals, test.N, check.Commentf("Test %d", i))
+		c.Check(t, check.DeepEquals, test.mat, check.Commentf("Test %d", i))
+	}
+}
+
+func (s *S) TestTriAtSet(c *check.C) {
+	t := &Triangular{blas64.Triangular{
+		N:      3,
+		Stride: 3,
+		Uplo:   blas.Upper,
+		Data:   []float64{1, 2, 3, 4, 5, 6, 7, 8, 9},
+		Diag:   blas.NonUnit,
+	}}
+	rows, cols := t.Dims()
+	// Check At out of bounds
+	c.Check(func() { t.At(rows, 0) }, check.PanicMatches, ErrRowAccess.Error(), check.Commentf("Test row out of bounds"))
+	c.Check(func() { t.At(0, cols) }, check.PanicMatches, ErrColAccess.Error(), check.Commentf("Test col out of bounds"))
+	c.Check(func() { t.At(rows+1, 0) }, check.PanicMatches, ErrRowAccess.Error(), check.Commentf("Test row out of bounds"))
+	c.Check(func() { t.At(0, cols+1) }, check.PanicMatches, ErrColAccess.Error(), check.Commentf("Test col out of bounds"))
+	c.Check(func() { t.At(-1, 0) }, check.PanicMatches, ErrRowAccess.Error(), check.Commentf("Test row out of bounds"))
+	c.Check(func() { t.At(0, -1) }, check.PanicMatches, ErrColAccess.Error(), check.Commentf("Test col out of bounds"))
+
+	// Check Set out of bounds
+	c.Check(func() { t.Set(rows, 0, 1.2) }, check.PanicMatches, ErrRowAccess.Error(), check.Commentf("Test row out of bounds"))
+	c.Check(func() { t.Set(0, cols, 1.2) }, check.PanicMatches, ErrColAccess.Error(), check.Commentf("Test col out of bounds"))
+	c.Check(func() { t.Set(rows+1, 0, 1.2) }, check.PanicMatches, ErrRowAccess.Error(), check.Commentf("Test row out of bounds"))
+	c.Check(func() { t.Set(0, cols+1, 1.2) }, check.PanicMatches, ErrColAccess.Error(), check.Commentf("Test col out of bounds"))
+	c.Check(func() { t.Set(-1, 0, 1.2) }, check.PanicMatches, ErrRowAccess.Error(), check.Commentf("Test row out of bounds"))
+	c.Check(func() { t.Set(0, -1, 1.2) }, check.PanicMatches, ErrColAccess.Error(), check.Commentf("Test col out of bounds"))
+	c.Check(func() { t.Set(2, 1, 1.2) }, check.PanicMatches, "mat64: triangular set out of bounds", check.Commentf("Test lower access"))
+	t.mat.Uplo = blas.Lower
+	c.Check(func() { t.Set(1, 2, 1.2) }, check.PanicMatches, "mat64: triangular set out of bounds", check.Commentf("Test upper access"))
+
+	c.Check(t.At(2, 1), check.Equals, 8.0)
+	t.Set(2, 1, 15)
+	c.Check(t.At(2, 1), check.Equals, 15.0)
+	t.mat.Uplo = blas.Upper
+	c.Check(t.At(1, 2), check.Equals, 6.0)
+	t.Set(1, 2, 15)
+	c.Check(t.At(1, 2), check.Equals, 15.0)
+}