38 patients (20 men, 18 women) underwent reoperation between July 1989 to September 1992 because of degeneration of bioprosthetic valves implanted in aortic or/and mitral position. Retrospective analysis revealed a mean implantation time of 116.5 +/- 31.5 months for the bioprostheses (median 116). At reoperation 63.2% of them had a single valve replacement, 36.8% a more complex cardiac procedure (double or triple valve replacement, valve replacement and coronary bypass grafting). 50% (n = 9) of the reoperation cohort were symptomatic (NYHA III), 16 (42.1%) were serious symptomatic (NYHA IV). All deaths were NYHA IV preoperatively. Early mortality was 18.4% (n = 7). Mean age at the time of first operation was 51 +/- 10.7, mean age at reoperation was 60.5 +/- 10.6. There was a significantly longer aortic clamp time (AKT, p = 0.0005) and bypass time (BPT, p = 0.0000) compared to first operation, also a significantly longer BPT of the deads confronted with the survivors (p = 0.0075). Bioprosthetic valves in mitral position were significantly longer implanted (p = 0.0416) than in aortic position. But there was no difference in implantation time of commercially available Carpentier-Edwards- or Ionescu-Shiley grafts. At reoperation we changed more than 95% of the degenerated valves to mechanical devices--corresponding to international tendencies. We discuss the early tissue degeneration of bioprosthetic valves and their increasing problem during reoperation.