In an attempt to answer the question as to whether or not aortocoronary bypass (ACB) does increase life expectancy of patients with coronary artery occlusive disease (CAOD), 4,766 consecutive patients undergoing ACB at the Texas Heart Institute from October, 1969 through June, 1975, were reviewed and followed for five and one half years. Overall early mortality was reduced from 9.7 percent during the first full year (1970) of the study to 3.3 percent during the last full year (1974). Early mortality in males (86.5 percent) was reduced to 3 percent during 1975, but in females only to 8.4 percent. However, late mortality in females was only 2.6 percent as compared to 3.4 percent in males. Long-term survival was similar for both males and females at five and one-half years when early mortality was considered. Males also experienced better symptomatic results than females with 90.3 percent of males remaining asymptomatic, while only 86.6 percent of females remained in this category. Early mortality increased as more vessels were bypassed, but late mortality decreased and symptomatic results improved as more complete revascularization was performed. Only 55 percent of late deaths were cardiac related. Actuarial comparison of this surgical series with the most comparable series in the literature of patients treated medically, demonstrated significant (P less than 0.001) increased survival in the surgical group as compared to medically treated patients at every year up to five and one-half years, for patients with double and triple vessel disease and for the entire series. In those patients with single vessel disease, the survival curves were similar to four years, following which survival was increased in the surgical patients at the end of the fifth and sixth reporting years. In summary, these data appear to suggest that surgical treatment of coronary artery occlusive disease does provide a favorable effect upon life expectancy.