Photo-cis-chlordane is accumulated by goldfish to a greater extent than cis-chlordane during a 16-hr exposure to 5 parts per billion (ppb) of each insecticide. However, the concentration of photo-cis-chlordane in vital organs (brain, nervous system, heart, liver, kidneys) during the 1-, 2-, and 4-day exposure is less than that of cis-chlordane. Only the swim bladder shows a much higher concentration of photo-cis-chlordane than cis-chlordane. These differences could hardly account for twice the higher toxicity of the former to goldfish. The transfer of pre-exposed fish to insecticide-free water resulted in faster elimination of photo-cis-chlordane than cis-chlordane; after five weeks, about 90% of the former was eliminated as compared with only 58% of the latter. High residues of both insecticides in the bile and the intestine during the initial period of exposure indicate a biliary route of elimination.