Accumulation and depletion of dieldrin in visceral fatty tissue of broilers

White rock chicks were fed a commercial crumbles ration with approximately 1.0 p.p.m. of the active ingreient of technical grade dieldrin added to it. The treated feed was replaced by uncontaminated feed at various times from two to eight weeks of age. Equations were computed to describe the accumulation and depletion of the insecticide in visceral adipose tissue. Accumulations in females were described by polynomial equations with significant quadratic coefficients which indicated that the rate of accumulation leveled off between six and eight weeks. Accumulation rates in males were essentially linear through ten weeks. After removal of dieldrin from the feed, insecticide depletion from fat could be described in both sexes by equations for power curves. Replacement of contaminated feed with uncontaminated feed by two or three weeks of age resulted in concentrations at control or background levels by eight weeks of age. Replacement of contaminated feed with non-contaminated feed at ages later than three weeks did not bring concentrations below those acceptable as non-hazardous for human consumption.