Approximately 200 female Swiss‐Webster mice, six to eight weeks of age, were divided into eight groups. Three of these groups were fed 10, 100, or 250 ppm Aroclor 1254. One group was treated with 1000 ppm lead. Three groups were exposed simultaneously to lead and Aroclor 1254 at concentrations of 10 ppm PCB + 1000 ppm Pb, 100 ppm PCB + 7000 ppm Pb, and 250 ppm PCB + 7000 ppm Pb. Control mice received deionized water and rat food only. All groups were exposed for a period of 12 wk, then bred, with exposure continued throughout gestation and lactation. Offspring were weaned onto the control diet at 3 wk of age.