A double-blind, randomised study of the antihypertensive efficacy of perindopril and ketanserin in 44 elderly noninsulin-dependent diabetic patients aged > or = 60 years was conducted. Blood pressure, blood biochemical and haematological parameters, plasma vasoactive hormones, urinary volume, electrolytes and microalbumin were measured at baseline, after a 4-week placebo period, and at intervals during 8 weeks of treatment with active drug. Electrocardiogram and echocardiogram data were also obtained. Dosages of perindopril used were 2 mg once daily for 4 weeks doubling to 4 mg once daily if a target blood pressure of < or = 160/90 mm Hg was not reached. Dosages of ketanserin were 40 mg twice daily increasing to 80 mg twice daily. Both drugs caused a small but statistically insignificant reduction in blood pressure. Although the response rates (supine systolic blood pressure reduction of > 10 mm Hg) were 54% for perindopril and 45% for ketanserin, target blood pressure (supine blood pressure 160/90 mm Hg) was reached in only 21% of perindopril and 20% of ketanserin recipients. Plasma creatinine and 24-hour urine sodium excretion increased in patients receiving ketanserin therapy. Glycaemic indices and the lipid profile did not change in either group, except for a reduction in plasma triglycerides in the ketanserin group. No changes in urinary microalbumin, electrocardiogram, or echocardiographic cardiac parameters were observed. It is concluded that in the present study neither drug provoked a significant blood pressure lowering effect and that serum creatinine increased in the ketanserin group.