In order to study the effects of eicosapentaenoic acid (Maxepa), Maxepa placebo and aspirin/dipyridamole combination on the clinical course and restenosis rate of atherosclerotic lesions after percutaneous transluminal coronary angioplasty 79 men and 29 women were randomly divided into three treatment groups and restudied angiographically within one year of the procedure. Angina recurred less in the Maxepa group than in the other groups, although not statistically so. Restenosis rate was significantly reduced in the Maxepa group (11%) compared to the placebo group (30%) but, while less, was not significantly lower than in the aspirin/dipyridamole group (17%). Maxepa treatment appears to reduce restenosis rate of coronary artery lesions after percutaneous transluminal coronary angioplasty and may be an acceptable and equally effective alternative therapy to aspirin/dipyridamole.