Background The early and late patency of the left internal thoracic artery (LITA) has been studied thoroughly, but less is known about coronary artery bypass grafts constructed from the right internal thoracic artery (RITA).Methods and Results Between January 1984 and March 1991, 413 patients on two surgical services had bilateral arteries or RITAs used as conduits for coronary artery revascularization.Sixty-seven patients (16%; 57 male and 10 female; mean age, 59 years) had graft angiography performed up to 97 months after operation (average, 27 months). In 38 patients, angiography was performed because of angina or other objective evidence of myocardial ischemia. For all 67 patients evaluated, patency of RITA grafts was 86% (58/67), and patency of LITA grafts was 89% (57/64). For grafts to the left anterior descending (LAD) coronary artery, overall patency was 90% (58/64), and there was little difference in patency of the RITA (93%, 28/30) versus the LITA (88%, 30/34). In contrast, the overall patency rate for internal thoracic arteries used to bypass vessels other than the LAD was 76% (45/59, P<.03 versus LAD); for these bypasses to arteries other than the LAD, RITA patency was 74% (26/35), and the patency of LITA grafts was 79% (19/24). Patency of RITA grafts routed through the transverse sinus was similar to patency of other bypasses to non-LAD vessels. Among 12 free grafts that used segments of the RITA, 10 were patent (83%). Of additional saphenous vein grafts, 69% (39/56) were patent at restudy.Conclusions This study supports the continued use of the RITA as a conduit for coronary artery revascularization.In our experience, the position of the target vessel is a more important determinant of graft patency than the side of the internal thoracic artery selected for use as a bypass graft. (Circulation. 1994;90(part 2):II-129-II-132.)