Angioplasty of the left coronary artery was undertaken in 65 patients with a chronic total occlusion of the right coronary artery (CLOSED RCA) and in 105 patients with no significant disease in the right coronary artery (OPEN RCA). No patient had attempted dilatation of the right coronary artery. CLOSED RCA versus OPEN RCA patients differed with respect to presence of poor left ventricular (LV) function (12% versus 4%, p = 0.07), number of stenoses per patient (2.2 versus 1.8, p less than 0.05), and stenoses in both left anterior descending and left circumflex artery (39% versus 23%, p less than 0.05). Procedural complications were low for both CLOSED RCA (one death) and OPEN RCA (one emergency bypass surgery) patients. At late follow-up (mean = 17 months), there was no difference in survival between CLOSED RCA and OPEN RCA patients (95% versus 93%, p = NS). Late cardiac events (death, bypass surgery, or myocardial infarction) occurred in 26% of CLOSED RCA patients and in 16% of OPEN RCA patients (p = ns). The absence of angina at follow-up was more frequent in OPEN RCA compared with CLOSED RCA patients (84% versus 61%, p less than 0.01). Angioplasty of the left coronary artery can be performed in CLOSED RCA patients without excessive procedural risk; however, at follow-up continued anginal symptoms are common.