Pregnant Sprague-Dawley rats, a fed a rapeseed protein diet (containing 0.2 mg glucosinolates/g protein concentrate) from day 0, showed no teratological effects on the 18th day. However, rats which were permitted to deliver, developed anorexia and weight loss after day 18. A reddish discharge, not blood, from the nose stained the fur of most animals fed rapeseed protein. A similar discharge developed in dams fed on lab chow but fasted after day 18. At delivery, dams would neglect the newborn during the first 24 h but would then resume their diet and litter care. Surviving litters of rapeseed-fed animals were comparable to controls in weight after 3 weeks. Vitamin supplementation did not prevent these effects. Force feeding the diet by gavage aggravated these toxic effects and prolonged the gestation period. No toxic effects were seen until day 18 of gestation when the rapeseed protein diet was fed to rats 3--6 weeks before mating. Control rats given glucosinolates by gavage did not show any adverse effects. The rapeseed protein diet had no effect on NMRI mice during pregnancy and on litter care up to 3 weeks.