Our previous work has suggested the presence of an insulin resistance in the adult offspring of streptozotocin-diabetic pregnant rats. In this study we used the euglycaemic hyperinsulinaemic clamp technique with an isotope-dilution method to define and quantify this postulated insulin resistance in adult offspring of streptozotocin-diabetic rats. Under basal conditions, these rats had a lower body weight than control rats, but their glucose and insulin concentrations were normal. During the hyperinsulinaemic clamp, the steady-state glucose infusion rate was significantly lower in the offspring of streptozotocin-diabetic rats than in both age- and weight-matched controls, indicating insulin resistance. Basal peripheral tissue glucose utilization was normal in the offspring of streptozotocin-diabetic rats, but the dose-response curve was shifted to the right:insulin concentrations causing half-maximal stimulation of glucose utilization were increased by about 60% in the offspring of diabetic rats; the maximal stimulation of glucose utilization, however, was unaltered. Basal hepatic glucose production was normal, but again, half-maximal suppression of glucose production occurred at insulin concentrations 50% higher than in control rats; in addition, the maximal suppression of glucose production was significantly decreased, even at insulin concentrations of 5700 microU/ml. These data are evidence for an insulin resistance in the adult offspring of streptozotocin-diabetic rats, characterized by: (1) a decreased insulin sensitivity by peripheral glucose-utilizing tissues, and, (2) a decreased sensitivity and responsiveness of the liver.