Results of direct coronary revascularization with 511 grafts in 213 patients from 1971 to 1974 are reviewed. To improve an early saphenous vein graft (SVG) patency of 84 per cent in the first 85 patients, we have used internal mammary artery grafts (IMAG), when possible, since January, 1973. In 1973 to 1974, 15 patients had SVG's only (36 grafts) and 113 received one or two IMAG's with or without additional SVG's (total 282 grafts); in 26 we used a crossed double IMAG. Forty-seven of 48 patients with unstable angina survived and did well. Flows in SVG's and IMAG's were comparable. Flows in right IMAG's to diagonal or marginal vessels were higher than in right IMAG's to right or left anterior descending (LAD) vessels. In 12 patients with both SVG and IMAG, there was no difference in flow response of either graft to vasoactive drugs. Survival, functional, and patency results with IMAG's were as good as or better than results with SVG's. We conclude that IMAG's yield higher patency and comparable flow rates to SVG's and should be used when the IMA approximates the recipient artery in size and when a high pulsatile free flow is measured from the end of the graft. IMAG's are also safe and feasible for unstable angina.