The overall prevalences of microvascular complications and their association with dietary, clinical, and metabolic characteristics have been studied in 503 Mexican type II diabetic subjects. Average daily dietary intakes were 1866 kcal, 46.5% as carbohydrate, 13.7 mmol cholesterol, 8.7 g fiber, and a polyunsaturated/saturated fat ratio of 0.98. Prevalence rates of microvascular and metabolic complications were as follows: background retinopathy 12.3%, exudative retinopathy 24.2%, proliferative retinopathy 8.1% (1% blind, 4% able to read large print only), 9.1% of patients had cataract, 15.9% nephropathy, and 40.8% peripheral neuropathy. In addition, 3.6% had experienced transient lower motor neuron facial paralysis and 0.2% oculomotor paralysis. Patients with retinopathy had a longer mean duration of diabetes, were less obese at the time of examination, and had higher initial and mean blood pressures and higher mean fasting blood glucose levels when compared with those without retinopathy. Similar differences were observed between groups with and without nephropathy except that mean blood glucose levels were similar in the two groups. The presence of peripheral neuropathy was associated with longer duration of diabetes, less obesity, higher mean blood pressure and mean blood glucose levels, and lower hemoglobin concentration. Patients treated with diet alone had significantly lower prevalences of all three microvascular complications but they also had significantly shorter duration of diabetes and lower mean blood glucose levels. However, multivariate analyses on the subgroup of 360 patients who had repeated fasting blood glucose measurements for at least 5 yr demonstrated associations between retinopathy and duration of diabetes, mean blood pressure and mean blood glucose, and percent calories from carbohydrate.(ABSTRACT TRUNCATED AT 250 WORDS)