The effects of pyrene on grazing and egg production of the ecologically important arctic copepods Calanus finmarchicus and Calanus glacialis were studied in the Disko Bay, Western Greenland. The effects of both passive uptake of pyrene by diffusion through membranes, and active uptake through ingestion of contaminated food were investigated for both species. Furthermore, the hatching success for eggs from exposed females and for eggs directly exposed to pyrene was also studied. There was no reduction in egg production in starved Calanus spp., which indicates that the uptake of pyrene through passive diffusion was limited. A significant reduction was observed in grazing and egg production for feeding C. finmarchicus exposed to the highest concentration of 100 nM pyrene within the experimental period. Furthermore, the time-dependent development in grazing and egg production was reduced for both species exposed to 100 nM, and we suggest that the effect of pyrene on these endpoints would increase with time. The observed difference in response time between the two species can be attributed to the differences in the amount of storage lipid and in their reproductive strategies. There was a lower hatching percentage for eggs from C. finmarchicus females exposed to 10nM pyrene, whereas the egg hatching percentage was not reduced for eggs exposed directly.