The pathophysiological processes of inflammation are involved in numerous diseases including cancer. Dysregulated activation of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) play important roles in the development of certain inflammatory diseases. Allyl isothiocyanate (AITC), which is present in many common cruciferous vegetables, has been used to treat many chronic diseases. The present study investigated the effect of AITC on lipopolysaccharide (LPS)-induced iNOS and COX-2 expression in murine macrophages. AITC suppressed LPS-induced iNOS expression, but did not suppress LPS-induced COX-2 expression, suggesting that AITC has a specific anti-inflammatory mechanism.