In complementary studies of the chronic effects of heptachlor on bluegills, four similar earthen ponds were treated once with different concentrations of heptachlor, and the fish in six plastic pools were routinely fed different levels of heptachlor. A fifth pond and two plastic pools were used as controls. Higher dosages resulted in higher concentrations of heptachlor residues, more pronounced tissue pathology, and higher mortality in the test fish. Heptachlor reached a maximum in the pond fish about 3 days after treatment, and could no longer be found in the fish or mud after 56 days. The fish fed continuous levels of heptachlor developed their highest residues at 56 days. Invertebrate populations in the two higher treatment level ponds were eliminated. Lesser effects appeared in the two lower concentrations. At the termination of the experiment, invertebrate populations in the treated ponds and the control were not significantly different, and had achieved or surpassed pretreatment levels. Degenerative liver lesions became pronounced in fish from the two higher exposure ponds, but a heavy infestation of trematode metacercariae in the fish of all the test ponds, except the control, clouded further interpretation of histopathological examinations. Pathology results from the fish in the feeding test, although inconclusive, tended to support the trends which were developing in the contact test. There was an inverse proportional relationship between growth of fish in the feeding test and the amount of heptachlor introduced. The control group showed the highest growth rate, and the groups with progressively higher intake of heptachlor had progressively lower growth rates.