dial 2 hour urine C-peptide were 63±24 μg/gm.Cr, and 57±32 pg/gm.Cr. in control subjects, and 91±62 μg/gm. Cr. and 65±34 μg/gm.Cr. in diabetics respectively. 2) There were significant positive correlations between 24 hour urine C-peptide and postprandial 2 hour urine C-peptide in control subjects and diabetics with the correlation coefficient of 0.74, 0.7 respectively. 3) The positive correlation were not observed between postprandial 2 hour urine C-peptide and postprandial increment of serm C-peptide in both subjects. This result suggests that measurement of postprandial 2 hour urinary C-peptide seems to be a simple and reliable measure to evaluate pancreatic B-cell function.