1. We examined the effect of the alpha-glucosidase inhibitor acarbose on urinary albumin excretion (UAE) in streptozotocin diabetic rats. 2. Treatment with acarbose for 8 weeks after induction of diabetes prevented the significant increase in UAE observed in untreated diabetic rats relative to nondiabetic controls. 3. Acarbose significantly reduced integrated glycemia, which correlated with albumin excretion rates, and exerts a salutary effect on diabetic renal dysfunction.