Male broiler chicks (Hubbard-Hubbard) were fed graded levels (0, 0.0006, 0.006, 0.03, and 0.120 p.p.m.) of hexachlorobenzene (HCB) for 8 weeks. Gel permeation chromatography was used to prepare tissue samples from fat, heart, gizzard, leg muscle, breast muscle, kidney, and liver for analysis by gas-liquid chromatography employing electron capture detection. No treatment related trends could be determined for body or organ weights. Histopathologic examination of brain, liver, testes, pancreas, small intestine, ventriculus, spleen, kidney, lung, and heart failed to reveal lesions in either control or treated groups. A linear relationship was found between HCB accumulation in tissues and the dietary HCB level. HCB accumulation was greatest in adipose tissue followed by the heart, gizzard, leg, kidney, liver, and breast. The biomagnification of HCB in adipose tissue of broiler chickens was 11 to 18 times the concentration in the diet. For example, a concentration of 0.03 p.p.m. of HCB in the diet resulted in the accumulation of HCB in adipose tissue in excess of 0.5 p.p.m. After 7 weeks, birds were taken off rations containing HCB. After a withdrawal period of five weeks, 0.5 p.p.m. of HCB remained in adipose tissue of birds that had been fed 0.12 p.p.m. of HCB.