Results from crosses between Goto-Kakizaki (GK) rats, which exhibit spontaneous non-insulin-dependent diabetes mellitus (NIDDM), and outbred nondiabetic Wistar rats have demonstrated an effect of maternal inheritance on diabetes in offspring of the first generation (F1). At 6 weeks of age, F1 offspring of sex-directed crosses exhibited plasma glucose values intermediate between GK and Wistar parents. Hyperglycemia in F1 rats born of female GK rats (F1GK) was more marked than in those born of female Wistar (F1W) rats. At 3 months of age, F1 rats showed a marked impairment of both glucose tolerance and insulin secretion, which was intermediate between GK and Wistar rats. Glucose intolerance was more pronounced in F1GK rats than in F1W. By contrast, insulin secretion in F1W rats was more deteriorated than in F1GK rats. No deletion in mitochondrial DNA was observed in the GK rats, which decreased the possibility of a mitochondrial inheritance effect as an explanation of our findings. These data support a polygenic model in diabetes inheritance of NIDDM and suggest that, in addition to genetic factors, a perturbed maternal metabolism can contribute to its inheritance.