Iodine was fed to turkey breeder hens during a 20-wk laying cycle to determine the appropriate dietary level to support reproduction and avoid toxicity. A basal diet that contained by analysis. 7 ppm iodine supported good hatchability of Large White turkey eggs. Supplementing 35 or 350 ppm iodine to the basal diet resulted in toxic effects (P less than or equal to .05) on hatchability. Feeding 350 ppm also depressed (P less than or equal to .05) egg weights, egg production, and eggshell water vapor conductance. Embryonic mortality data indicated that toxic effects of iodine on embryos occur principally during the 1st wk of incubation and immediately prior to and during pipping. It was concluded that iodine toxicity may occur in Large White turkey breeder hens when 350 ppm are fed in the diet.