Insulin is an important regulatory hormone in the control of fetal growth. In a fetal rabbit model, a non-ruminant species, the effects of insulin deprivation on glucose, growth and protein metabolism were studied. The fetuses of 10 pregnant New Zealand white rabbits in one uterine horn received a subcutaneous injection on day 25 of gestation (term = 30 days) of 0.1 mg streptozotocin (STZ)/gm fetal weight. The fetuses in the opposite horn received a sham injection of buffer. The dams were then killed on day 29. The fetal insulin concentration was depressed by 38%, and the serum glucose concentration was elevated by 28% in animals given STZ when compared to control animals. Fetal weights, carcass weights and skeletal growth, as measured by crown-rump length and tibial length of STZ-treated fetuses, were significantly reduced by 7-13%. However, organ weights were not significantly different, except for the kidneys which were 17% lighter. Protein and mineral contents of the carcasses were also reduced compared to the control fetuses. Thus, insulin deprivation in fetal rabbits results in significant growth impairment in a pattern similar to that of human asymmetric intrauterine growth retardation.