Fathead minnows (Pimephales promelas) were exposed during a partial chronic toxicity study to endrin concentrations in the water or food, or both, for 300 days encompassing reproduction. Tissue residues were analyzed at preset intervals for first-generation fish, and were also determined for embryos, larvae at hatch, and 30-day progeny. Gas-chromatographic and liquid-scintillation techniques were used to monitor the contribution of endrin from each source. The food was clams that had accumulated 14C-endrin when exposed to an endrin water concentration similar to that to which the fish were exposed. Higher endrin tissue residues were accumulated from the water than from food. Maximum concentration factors were 0.8 from the food and 13,000 from the water. Residues contributed by endrin in the food were additive to those from the water at all life stages. Endrin in the food (0.63 ppm) significantly reduced survival of the fathead minnows, and fish exposed to both endrin sources had lower survival than those exposed to either source alone. Endrin residues in embryos and larvae were highest and larval survival lowest for progeny of adults exposed to endrin in both food and water. Survival of 30-day progeny was significantly reduced at all test exposures (0.63 ppm in the food, water exposures of 0.14 and 0.25 ppb, and all combinations of food and water exposure).