The subcellular distribution of gamma-glutamylamino-transferase (EC 2.3.2.2) and transglutaminase (EC 2.3.2.1) has been investigated in rat brain tissue fractionated by a centrifugation and sedimentation technique. Neither of these enzymes was enriched in the synaptosomal fraction. Comparing the in vitro grown astrocytes with synaptosomes, we find that both of these enzymes may possibly be more important in the glial element of the synaptic region. gamma-Glutamylaminotransferase is most abundant in capillaries, confirming previous reports.