From 1976 to 1987, 877 patients, aged 13 to 80 years, underwent valve replacement with a Carpentier-Edwards porcine bioprosthesis--330 aortic, 421 mitral, and 126 multiple replacements. Patients were divided into 4 age groups, according to their age at the time of surgery: group I, less than 45 years (190 patients), group II, 45 to 54 years (203 patients), group III, 55 to 64 years (304), and group IV, 65 to 80 years (180 patients). Follow-up was 97.5 complete, averaged 85 months, and totalled 5624 patient-years. There were 79 early deaths (9%), and 181 late deaths. Overall survival was 80% and 64% at 5 and 10 years. Operative mortality increased significantly with age, and late survival was significantly better for group I. Intrinsic structural deterioration was the most common cause for reoperation and was responsible for 91% of the 143 reoperations. Incidence of intrinsic structural deterioration and of reoperation decreased significantly with increasing age, with respective freedom rates at 10 years of 57 and 54 in group I compared to 93 and 92% in group IV. Freedom from treatment failure (including early deaths, valve-related deaths, and valve-related complications with permanent disability) was similar for all 4 groups ranging from 78 to 85%, without any correlation with age of the patient. At last follow-up, a similar proportion of patients of each group remained asymptomatic, patients in functional class I ranging from 50 to 55%. Thus, age is a major determinant of durability of bioprostheses, but it does not appear to have a significant role in the overall success of valve replacement.