Bioelectrical impedance is a technique allowing a quick, repeatable and reliable assessment of body composition. This method was applied to detect total body water (TBW), fat (FAT) and fat-free mass (FFM) in 80 normal subjects, 65 diabetic (45 insulin-dependent [IDD], 20 non insulin-dependent [NIDD]) and 34 uremic diabetic patients (20 IDD, 14 NIDD) submitted to hemodialysis three times a week. Uremic patients were tested at the end of the dialytic session. Multivariated analysis adjusted for age, sex and disease showed the following results: body mass index (BMI) increased with age (p < 0.005) and in the presence of NIDD (p < .001); TBW was lower in nephropathic patients (p < 0.05) and in the female sex (p < 0.0001); FFM decreased with age (p < 0.005), female sex (p < 0.0001) and in nonuremic NIDD (p < 0.001). Correspondingly FAT increased with age (p < 0.005), female sex (p < 0.0001) and in nonuremic NIDD (p < 0.001). Sixteen uremic subjects, randomly selected from both IDD and NIDD groups, tested at the beginning and at the end of the same hemodialytic session, showed a significant decrease of TBW which corresponded to the correction of their overhydratation. In our patients uremia does not seem to influence the nutritional status and the bioelectrical analysis could be applied to determine the real dry weight in hemodialyzed diabetic patients.