A median mortality of 120 ± 30 days occurred among juvenile Atlantic salmon (Salmo salar), fed dry fish food containing 2.7, 5.7, 2.8, and 9.1 uMg/g wet weight of 2,8-di-, tri-, tetra-, and octachlorodibenzofuran, respectively (1). Only octachlorodibenzofuranx was detected in the dead fish, and the level was 0.03 ug/g in the muscle and 0.21 ,Ag/g in the gut (both values on wet weight basis). The fate of the lower chlorinated dibenzofurans was not known and additional experiments, described in this paper, were carried out with immature brook trout (Salvelinus fontinalis), fed relatively high levels of 2,8-dichlorodibenzofuran. ExperimentalThe preparation of 2,8-dichlorodibenzofuran was carried out as described (2). Three crystallizations were necessary to remove tri-and tetrachlorodibenzofuran from the product.