The effect of the angiotensin converting enzyme inhibitor enalapril on serum lipids, apolipoproteins, and lipoproteins was studied in 21 patients with mild essential hypertension. The drug was administered at a dosage of 2.5 to 10 mg daily for 12 weeks. Enalapril significantly decreased the very low-density lipoprotein (VLDL) fraction at eight and 12 weeks. The apolipoprotein (apo) A-I and A-II fractions were significantly increased by 10% and 7.8%, respectively, at 12 weeks. The apo B fraction and the apo B/apo A-I ratio were significantly decreased at eight weeks (8% and 17%, respectively) and at 12 weeks (11% and 19%, respectively). Unchanged were the total cholesterol level, the lipoprotein cholesterol level, the triglyceride level, apo C-II, apo C-III, apo E, and the apo A-I/apo A-II ratio. This study confirmed that enalapril is an effective antihypertensive drug with a favorable effect on the lipid profile.