With the aromatic retinoic acid analog Tigason oral and intravenous pharmacokinetic studies have been performed in 5 normal volunteers. Simultaneous fitting of single i. v. and oral data to a three-compartment model assuming first-order absorption was possible. Using Nonlin parameter estimates of the single-dose data, one is able to predict the decline in plasma levels of parent drug following cessation of a 10 days multiple dosing regimen up to 24 hours. The model is however unable to predict a phase of prolonged elimination observed beyond 24 hours. Moreover in 5 patients, who underwent chronic therapy (8-15 months), substantial plasma levels of both unchanged drug and main metabolite (corre­ sponding carboxylic acid) were observed up to 140 days after cessation of the therapy. ! Uwagi: Oprawa nieznacznie porysowana. Brzegi stron zakurzone.