Seventeen and 38 dipper eggs were collected from nests in south-west Ireland during 1990 and 1991 respectively and analysed for organochlorine insecticides, PCBs and mercury. Mercury occurred above the detection limit (0.01 p.p.m.) in over 70% of eggs in 1990 and 12% of eggs in 1991. DDT was not recorded, but its main derivative, DDE, was the most common organochlorine detected, with a mean level in contaminated eggs of 0.68 p.p.m. and a maximum of 3.20 p.p.m. TDE was detected only in eggs collected in 1990. HCB was recorded in only a single egg in 1990, but increased to 30% in 1991. The level of dieldrin (HEOD) in eggs differed between years. HCH was the least recorded organochlorine. There was a significant difference in PCB contamination between years, and the highest levels were recorded at moorland sites. The results are discussed in the context of monitoring mercury and organochlorines in freshwater ecosystems in Ireland.