A total of 216 male Sprague‐Dawley rats were used. Animals were injected IP every 3 days for 29 days for a total of 9 injections with 0, 1.0 or 2.5 mg Cd/kg body wt. Total cumulative doses were 0, 9.0 or 22.5 mg Cd/kg body wt. Twenty‐four hrs after the last Cd injection (day 30), each animal was subjected to an acute sublethal total‐body exposure of 0, 362 or 543 rads of gamma (60Co) irradiation at a dose rate of 304 rads/min. Eight rats from each of the 9 groups were sacrificed by cardiac exsanguination on post‐irradiation day 1, 7 or 21.