We studied 112 type 2 diabetic patients. Fourteen patients had frank proteinuria, and 37 of the remaining 98 had microalbuminuria which was more frequent in men than in women ( P<0·02). Hypertension was found in 47 of the patients, equally distributed between sexes. Male diabetics with microalbuminuria had higher systolic blood pressure than diabetics without microalbuminuria ( P<0·02). Body mass index was higher in both sexes with hypertension compared to patients without hypertension. In the hypertensive men plasma C-peptide values were higher compared to patients without hypertension ( P<0·01) irrespective of the presence of microalbuminuria. A positive correlation between blood pressure and C-peptide was found ( P<0·01) in the men. We suggest that gender should be taken into account in the analysis and interpretation of microalbuminuria in type 2 diabetes.