Previtellogenic oocytes from Atlantic salmon were exposed to different concentrations of PCB77 using an in vitro agarose culture system for 3, 7 and 14 days. Overall, our results show time- and concentration-specific effects of PCB77 on key steroidogenic enzyme, P450scc and protein, StAr at the mrNA level, as well as protein level using immu-nohistochemical analysis.