Doses of 3 and 10 mg/kg/day acitretin were orally administered to female Wistar rats over a period of 6 weeks. Phospholipid classes, P-450 content, aminopyrine-N-demethylase (ADM) and 7-ethoxyresorufin-O-deethylase (7-ERO-D) activities were determined in the liver microsomes of the treated animals. Both dosages caused statistically significant alterations in rat liver microsomal phospholipid composition which may be associated with changes in the metabolic activity, ionic transport, cell-cell interaction and other processes of the hepatic cellular components. Furthermore, statistically significant alterations of P-450 isozyme activities were induced by both dosages. Our data suggest a possible interaction of acitretin with other drugs and endogenous substances metabolized by these enzyme systems.