The effects of long-term cilazapril therapy on glucose tolerance and serum lipid profiles were investigated in 19 hypertensive patients: seven with normal glucose tolerance and 12 with glucose intolerance (including three patients with noninsulin-dependent diabetes). Cilazapril was administered once daily for a mean duration of 6.4 months. A 75-g oral glucose tolerance test was performed before and during long-term therapy with cilazapril. Cilazapril produced satisfactory control of blood pressure in both patient groups during long-term therapy. It was well tolerated by all patients. Neither fasting nor postglucose-load venous plasma glucose levels were altered in either group of patients, and no patients with normal glucose tolerance developed diabetes mellitus during the study. There were no significant changes in the insulinogenic index (delta IRI/delta BS at 30 min postglucoseload) in patients with normal or impaired glucose tolerance. No significant changes in fasting levels of serum cholesterol, HDL-cholesterol, LDL-cholesterol, and triglycerides were observed in either group. These results suggest that effective long-term cilazapril therapy does not compromise glucose or lipid metabolism in hypertensive patients. Cilazapril may have a clinical advantage in that it can be given to hypertensive patients without concern that it might alter their serum lipid concentrations or impair glucose tolerance.