The aim of this study was to determine the factors associated with diabetic peripheral neuropathy and more particularly its relation to precisely assessed microangiopathy. Peripheral neuropathy was assessed in 135 diabetic patients: 28 insulin-dependent diabetes mellitus (IDDM), 85 non-insulin-dependent diabetes mellitus (NIDDM), and 22 insulin-treated NIDDM patients, on the basis of both clinical findings and extensive electrophysiological testing (four motor nerves and four sensory nerves, and right and left Hoffmann's reflex), using a total of 20 parameters. The percentage of women with severe clinical neuropathy was significantly higher than that of men, and the clinical neurological stage correlated significantly with age and duration of diabetes. According to multivariate analysis the clinical stage correlated only with gender and duration of diabetes. Several electrophysiological parameters were significantly more abnormal in women and correlated with age, type and duration of diabetes, and recent glycemic control. The multivariate analysis showed that 17 electrophysiological parameters correlated with duration of diabetes, nine correlated with age, seven with glycemic control, and only one with gender. The presence of clinical neuropathy also correlated with presence of retinopathy, arterial hypertension, macroangiopathy, and biological signs of nephropathy. All the electrophysiological parameters were significantly more abnormal in patients with retinopathy or macroangiopathy than in patients without these complications. Separate parameter analysis showed that at least one abnormal electrophysiological parameter was almost always found in patients with retinopathy, macroangiopathy, or incipient nephropathy, but abnormalities were also found to a slightly lesser extent in patients without these complications. Multivariate analysis showed that when duration of diabetes, retinopathy, macroangiopathy, and biological signs of nephropathy were introduced into the model, 11 electrophysiological parameters correlated with duration of diabetes, 11 with retinopathy, seven with macroangiopathy, and five with a sign of nephropathy. This study demonstrates that age and glycemic control have an effect, and diabetes duration a major effect on peripheral nerve function. It suggests that vascular factors may participate in the development of nerve lesions.