Background: Whether the use of the radial artery (RA) can improve clinical outcomes in coronary artery bypass graft surgery remains unclear. The ART (Arterial Revascularization Trial) was designed to compare survival after bilateral internal thoracic artery (BITA) over single left internal thoracic artery (SITA). In the ART, a large proportion of patients (≈20%) also received an RA graft instead of a saphenous vein graft (SVG). We aimed to investigate the associations between using the RA instead of an SVG to supplement SITA or BITA grafts and outcomes by performing a post hoc analysis of the ART. Methods: Patients enrolled in the ART (n=3102) were classified on the basis of conduits actually received (as treated). The analysis included 2737 patients who received an RA graft (RA group; n=632) or SVG only (SVG group; n=2105) in addition to SITA or BITA grafts. The primary end point was the composite of myocardial infarction, cardiovascular death, and repeat revascularization at 5 years. Propensity score matching and stratified Cox regression were used to compare the 2 strategies. Results: Myocardial infarction, cardiovascular death, and repeat revascularization cumulative incidence was 2.3% (95% confidence interval [CI], 1.1–3.4), 3.5% (95% CI, 2.1–5.0), and 4.4% (95% CI, 2.8–6.0) in the RA group and 3.4% (95% CI, 2.0–4.8), 4.0% (95% CI, 2.5–5.6), and 7.6% (95% CI, 5.5–9.7) in the SVG group, respectively. The composite end point was significantly lower in the RA group (8.8%; 95% CI, 6.5–11.0) compared with the SVG group (13.6%; 95% CI, 10.8–16.3; P =0.005). This association was present when an RA graft was used to supplement both SITA and BITA grafts (interaction P =0.62). Conclusions: This post hoc ART analysis showed that an additional RA was associated with lower risk for midterm major adverse cardiac events when used to supplement SITA or BITA grafts. Clinical Trial Registration: URL: https://www.situ.ox.ac.uk/surgical-trials/art . Unique identifier: ISRCTN46552265.