The biliary excretion of some perhexiline metabolites has been assessed in male Wistar rats with biliary cannulation. 2. After intragastric administration of perhexiline maleate (2 mg/kg body weight) multiple perhexiline metabolites were detected in bile. 3. When aliquots of this metabolite-laden bile were administered intraduoduodenally to further 'recipient' rats with biliary cannulation, similar metabolites were detected in the bile of these rats, but at reduced concentrations equivalent to 30-35% of those present in the bile of 'donor' rats. 4. These findings indicate that in the male Wistar rat, there may be substantial enterohepatic circulation of some perhexiline metabolites.