To assess the validity of the steady-state plasma glucose (SSPG) method using octreotide (Sandostatin), we compared the SSPG method with the euglycemic hyperinsulinemic clamp technique in ten non-obese, insulin-dependent diabetic patients. The SSPG method was performed by intravenous infusion of octreotide (0.5 microgram/min), insulin (2 mU/kg/min) and glucose (9 mg/kg/min) for 180 min. Octreotide suppressed endogenous growth hormone, glucagon and insulin secretion. A steady state condition was reached by 90 min, and the mean value of SSPG at 150 and 180 min was used as the index of insulin sensitivity. The euglycemic hyperinsulinemic clamp technique was performed with an artificial endocrine pancreas (Biostator), and insulin sensitivity was expressed as the glucose disposal rate (GDR) from 150-180 min. There was a significant correlation (r = 0.91, p < 0.001) between the results of the two methods. In conclusion, measurement of SSPG, using octreotide to suppress endogenous insulin secretion, is a reliable method to assess insulin sensitivity in man.