Percutaneous transluminal coronary angioplasty is widely considered to be an acceptable and less expensive alternative to bypass surgery in carefully selected patients. We compared expenditures related to cardiac care for 79 unselected patients undergoing coronary angioplasty with expenditures for 89 unselected patients undergoing elective coronary bypass surgery without a previous attempt at angioplasty. All the patients had single-vessel disease. The mean aggregate one-year monetary outlay was 15 per cent lower in the angioplasty group than in the bypass-surgery group. A major component of the expense of angioplasty was the treatment of restenosis in the 33 per cent of patients in this group in whom this late complication occurred. We conclude that percutaneous transluminal coronary angioplasty has potential for reducing expenditures for cardiac revascularization and that a further reduction may be obtainable when the rates of restenosis are improved.