Background: The fate of bioprostheses (BP) and mechanical prostheses (MP) after valve re-replacement for bioprostheses is not well-documented. This research compares the late fate of these two valve types after valve re-replacement for structural valve deterioration (SVD) of a bioprosthesis. Methods: Between 1975 and 2000, 298 patients had successful aortic valve re-replacements (AVRR) (BP n = 149, average age = 67.1 ± 12.3 years; MP 149, 58.9 ± 10.9) and 442 patients had successful mitral valve re-replacements (MVRR) (BP 155, 65.8 ± 14.1; MP 287, 60.8 ± 11.7) after SVD of a previous BP. Follow-up was five years in all groups. Results: (1) Aortic position (AVRR): Survival favored MP over BP overall, at 10 years (70.3 ± 5.4% vs 56.7 ± 5.7%, p = 0.0220). This survival advantage was seen to be significant only in patients less than 60 years of age (at 10 years, 85.3 ± 4.9% vs 59.2 ± 9.8%, p = 0.038). No significant difference in survival between the two valve types was observed in patient age groups greater than 60 years of age. Freedoms from valve-specific complications, including reoperation for SVD-thrombosis, major thromboembolism and hemorrhage, and valve-related mortality were not significantly different between the two groups overall. (2) Mitral position (MVRR): Survival favored MP over BP overall (58.6 ± 4.2% vs 42.1 ± 5.2%, p = 0.0011), and in patients greater than 70 years of age (32.8 ± 8.9% vs 16.7 ± 7.1%, p = 0.008). Freedoms from valve-specific complications and valve-related mortality favored MP over BP. Conclusions: There was no clinical performance difference between mechanical and bioprosthetic valves in patients greater than 60 years of age upon AVRR. Mechanical valves generally outperformed bioprosthetic valves in all age groups in MVRR.