Recently, a dramatic decline in the cumulative incidence of diabetic nephropathy (less than 10% after 25 years of diabetes) has been reported in IDDM patients diagnosed between 1961 and 1980. In a clinic based study we assessed recent trends in the incidence of diabetic nephropathy. All 356 patients in whom IDDM was diagnosed before the age of 41 years between 1965 and 1979, identified in 1984 were followed to 1991 or to death. The cumulative incidence of diabetic nephropathy (urinary albumin excretion 300 mg/24 hours in two out of three consecutive samples) after 15 years of diabetes and in 1991 were (cumulative incidence (SE)): 18 (4)% and 35 (5)% (onset of diabetes 1965-69, n = 113), 20 (4)% and 35 (5)% (onset of diabetes 1970-74, n = 130), and 16 (5)% (onset of diabetes 1975-79, n = 113), respectively (ns). The mean (SE) haemoglobin A1c measured yearly beginning in 1984 was higher in patients with nephropathy (9.4 (0.1)%), and persistent microalbuminuria (8.9 (0.1)%) than in patients with normoalbuminuria (8.5 (0.1)%, (p < 0.001)). Our study revealed no decline in the cumulative incidence of diabetic nephropathy with increasing calendar year of diabetes onset. This may in part be explained by poor metabolic control and a high prevalence of smokers (58-71%).