The antihypertensive efficacy of enalapril and its effects on renal function and glucose homeostasis were investigated in 9 hypertensive patients with non-insulin-dependent diabetes mellitus. Enalapril therapy produced a significant fall in blood pressure (BP) (p < 0.05) and a significant increase in renal blood flow (p < 0.05) without a change in glomerular filtration rate. Furthermore, fasting plasma glucose was significantly reduced (p < 0.01). Similarly, M value, as an index of plasma glucose control in diabetes, was significantly reduced from 19.6 to 10.1 (p < 0.01). These findings suggested that the angiotensin-converting enzyme inhibitor enalapril was effective in reducing BP and improving renal function, and might improve glucose homeostasis in hypertensive diabetics.