The aim of this cross-sectional study was to establish the prevalence of renal involvement and to identify associations with its most important possible risk factors in a group of patients with Type II diabetes mellitus, representative of the population living in Catalonia. One thousand two hundred and three patients (47% males, mean age: 61 +/- 6 years, diabetes duration 9 +/- 6 years) were studied. Overnight urine samples were collected to determine urinary albumin excretion (UAE). If UAE was > 15 micrograms/min, a new 24-h urine collection for UAE measurement to establish the existence of microalbuminuria (20-200 micrograms/min) or macroalbuminuria (> 200 micrograms/min) was obtained. Clinic and metabolic evaluations were also performed. The prevalence (%) of microalbuminuria, macroalbuminuria and hypertension were, respectively, 23. 1, 5.4 and 42. In comparison with normoalbuminurics, patients with microalbuminuria were predominately male (P < 0.03), with a significantly higher systolic (P < 0.001) and diastolic (P < 0.001) blood pressure and body mass index (P < 0.001). The prevalence of smokers (former + current) was higher in patients with microalbuminuria (43 vs 32%, P < 0.025). Moreover, patients with nephropathy had more prevalence of retinopathy (P < 0.001), neuropathy (P < 0.001), peripheral angiopathy (P < 0.001) and coronary disease (P < 0.001). The prevalence of microalbuminuria in Type II diabetes in Catalonia is similar to that observed in other european countries. The existence of microalbuminuria is associated with several diabetic complications, as well as tobacco consumption and obesity.