In order to evaluate the influence of glycemic control and hypertension on the development of diabetic nephropathy, we measured urinary excretion of albumin (AER) and other microproteins in non-insulin-dependent diabetes mellitus (NIDDM), and reexamined the 103 patients who had had AER less than 300 micrograms/min at the initial study 12-18 months later. AER in the patients with HbA1c greater than or equal to 7.5% increased significantly in both the normoalbuminuric (AER less than 30 micrograms/min) and microalbuminuric (30-300 micrograms/min) groups, whereas no significant change in AER was observed in the patients with HbA1c less than 7.5%. In the microalbuminuric group, AER in both hypertensive and normotensive patients increased significantly. In this group, the change in AER correlated positively with the change in alpha 1-microglobulin (alpha 1M). These results indicate that glycemic control has a greater influence on the development of nephropathy in its early stage than hypertension and that alpha 1M is as a good predictor of nephropathy as albumin.