Nitric oxide (NO) is an important inhibitoryneurotransmitter in the gut. Alterations in NO mediatedresponses have been described in diabetic animals. Thepresence of nitric oxide synthase (NOS) reflects the potential for NO synthesis and is found inneurons in the myenteric plexus. The aim of this studywas to determine changes in nitric oxide synthase (NOS)expression in the myenteric plexus of thegastrointestinal tract of diabetic rats at three months ofstreptozotocin-induced diabetes, compared to age matchedcontrols, using immunohistochemistry. Diabetic animalsshowed a decrease in NOS expression in the antrum, with 59.1 ± 7.3% of neurons beingpositive for NOS in diabetes compared to 81.2 ±4.7% in controls (P < 0.05). NOS expression induodenum, ileum, and colon of diabetic animals was notstatistically different from controls. Decreased expression of NOS inantrum may contribute to altered gastric emptyingobserved in diabetics.