In this placebo-controlled, randomized double-blind, parallel study the effects of the fixed captopril 50 mg + hydrochlorothiazide (HCTZ) 25 mg combination on plasma lipids were assessed in 42 hypertensive, type IIa or IIb hyperlipidaemic patients on diets. Some patients received oral hypolipidaemic treatment and some did not. Blood pressure and plasma lipids levels were measured before and after 1, 2 and 3 months of treatment. From the first month onward blood pressure decreased more in the treated group than in the placebo group (P < 0.05). Neither the combination nor the placebo altered the following parameters of lipid metabolism: total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, apolipoprotein A1 and apolipoprotein B. The combination was well tolerated; 2 patients in each group had one or several adverse events. The results of this study show that treatment with the captopril-HCTZ combination in hypertensive, hyperlipidaemic patients has no influence on the normolipidaemic effects of diet and lipid-lowering treatment.