The rate and efficiency of uptake from food, the distribution in selected tissues, and the rate of elimination, of 14C‐p,pˈ DDT and 14C‐dieldrin in rainbow trout were investigated during and after a minimum of 140 days of exposure. Growth of fish during 140 days of exposure was not affected by insecticide exposure. However, both DDT and dieldrin significantly increased lipogenesis during this period. Total residue accumulation was dose‐dependent, and those fish exposed to 0.2 mg/kg per week of either DDT or dieldrin, or to 1.0 mg/kg per week dieldrin apparently had reached the equilibrimn state after 140 days of exposure. Fish accumulated 20–24% of the available dietary DDT and 9–11% of the available dietary dieldrin. Generally, there was an approximately linear increase in the residue concentration of a tissue, followed by an equilibrium state during which the residue content remained virtually constant with continued exposure to the insecticide. The predicted time required for rainbow trout to eliminate 50% of total body DDT or dieldrin is 160 days or 40 days, respectively. Significant interaction between DDT and dieldrin was evident. In the pyloric caecae, the presence of dieldrin increased the rate of accumulation of DDT; conversely, the presence of DDT decreased the rate of accumulation of dieldrin. The presence of dieldrin decreases, if not inhibits, the elimination of DDT while the presence of DDT has no effect on the elimination of dieldrin. Interaction may effect total residue accumulation in rainbow trout.