The estuarine fish, spot (Leiostomus xanthurus), was exposed to 0.27, 0.52, 1.01, 1.99, and 3.87 μg/liter technical grade heptachlor (65% heptachlor, 22%trans‐chlordane, 2%cis‐chlordane, 2% nonochlor, and 9% unidentified compounds) for 24 days in a flowthrough bioassay, followed by 28 days in heptachlor‐free seawater. Concentrations of heptachlor, heptachlor epoxide, andtrans‐ andcis‐chlordane in edible tissues were monitored at day 3 and weekly thereafter throughout the bioassay and at the end of the postexposure period. All four chemicals were accumulated by spot. Maximum concentrations of heptachlor were observed on day 3; maximum concentrations of the other three compounds were observed on day 17. The average bioconcentration factors for heptachlor andtrans‐chlordane were 3,600 and 4,600, respectively. Only 10% or less of the maximum concentrations of heptachlor, heptachlor epoxide, andtrans‐chlordane accumulated during the exposure period remained after 28 days in pesticide‐free seawater; an average of 35% of thecis‐chlordane remained. Relative total amounts of heptachlor andcis‐chlordane changed during the exposure and post‐exposure periods. Nearly all of the heptachlor was eliminated or metabolized to its epoxide.Cis‐chlordane, which averaged 4–7% of the total residues (chlordanes and heptachlors) in edible tissues during the exposure, increased to 18–23% of the total residues by the end of the postexposure period.