diff --git a/transport.go b/transport.go
index b14635b..258be39 100644
--- a/transport.go
+++ b/transport.go
@@ -11,6 +11,12 @@ type Transport struct {
 	APIKey string
 }
 
+// NewTransport constructs and returns a new Transport struct that includes the
+// given API key as a header in each request.
+func NewTransport(apiKey string) *Transport {
+	return &Transport{APIKey: apiKey}
+}
+
 // Client returns an HTTP client that will include the API key in the request,
 // and is safe for concurrent use by multiple goroutines.
 func (t *Transport) Client() *http.Client {
diff --git a/transport_test.go b/transport_test.go
index cdf3a1b..9c26d27 100644
--- a/transport_test.go
+++ b/transport_test.go
@@ -1 +1,11 @@
 package anthropic
+
+import "testing"
+
+func TestNewTransport(t *testing.T) {
+	apiKey := "test-api-key"
+	transport := NewTransport(apiKey)
+	if transport.APIKey != apiKey {
+		t.Errorf("transport.APIKey = %q, want %q", transport.APIKey, apiKey)
+	}
+}