Cryptolepine is the major alkaloid of the West African shrub, Cryptolepis sanguinolenta. Cryptolepine has been shown to inhibit nitric oxide production, and DNA binding of Nuclear Factor-kappa B following inflammatory stimuli in vitro. In order to validate the anti-inflammatory property of this compound in vivo, we investigated its effects on a number of animal models of inflammation. Cryptolepine (10-40 mg/kg i.p.) produced significant dose-dependent inhibition of the carrageenan-induced rat paw oedema, and carrageenaninduced pleurisy in rats. These effects were compared with those of the non-steroidal anti-inflammatory drug indomethacin (10 mg/kg). At doses of 10-40 mg/kg i.p., cryptolepine inhibited lipopolysaccharide (LPS)-induced microvascular permeability in mice in a dose-related fashion. Oral administration of up to 40 mg/kg of the compound for four consecutive days did not induce gastric lesion formation in rats. Analgesic activity was also exhibited by cryptolepine through a dose-related (10-40 mg/kg i.p.) inhibition of writhing induced by i.p. administration of acetic acid in mice. The results of this study reveal that cryptolepine possesses in vivo anti-inflammatory activity.