We inquired whether the type of diabetic glomerulosclerosis, diffuse or nodular, is of value as an alternative to microalbuminuria in predicting later progression of renal disease. To answer this question, we conducted a retrospective cohort study in eleven Japanese non-insulin-dependent diabetes mellitus patients with normo- to microalbuminuria. Nodular diabetic glomerulosclerosis was found in six patients, and diffuse diabetic glomerulosclerosis in five patients. The mean follow-up period was 41.5 months (range 12-65). Three patients developed persistent proteinuria and one developed chronic renal failure. Mean level of serum creatinine in all patients was elevated from 0.97 +/- 0.23 mg/dl (SD) to 1.10 +/- 0.37 mg/dl (P = 0.098). The rate of increase in serum creatinine was 0.068 +/- 0.115 mg/dl/year in nodular diabetic glomerulosclerosis, and 0.023 +/- 0.069 mg/dl/year in a diffuse one. No difference was found between these two types of diabetic glomerulosclerosis (P = 0.445). We conclude that in normo- to microalbuminuria diabetic nephropathy the type of diabetic glomerulosclerosis, diffuse or nodular, is not necessarily an alternative to microalbuminuria in predicting its later progression in Japanese non-insulin-dependent diabetes mellitus patients.