The present study was carried out to investigate the effect on tissue vitamin A levels in rats exposed to 3,3',4,4'-tetraCB (CB-77), 2,3',4,4',5-pentaCB (CB-118), 3,3',4,4',5-pentaCB (CB-126), and 2,2',4,4',5,5'-hexaCB (CB-153). The obtained results show that hepatic vitamin A levels are reduced both in male and female rats following dietary exposure to individual PCB congeners for 13 weeks. However, there are pronounced potency differences between congeners. Compared to TCDD, the hepatic vitamin A reducing potencies of CB-126, CB-77 and CB-153, are 0.05, 0.0001 and 0.00001, respectively, in male rats. Compared to male rats, female rats are equally sensitive to hepatic vitamin A reduction both by TCDD and dioxinlike CBs. Effects on renal and pulmonary vitamin A levels vary between CBs and between sexes.