Original Article Objective: The ideal valve substitute in children does not exist. Biologic and bioprosthetic valves do not require anticoagulation, however their use is complicated by accelerated degeneration and requirement for reoperation. We examine results following mitral (MVR) or aortic (AVR) replacement with biologic and bioprosthetic valves at our institution. Methods: Medical records of children who underwent AVR or MVR from 1986 to 2006 were reviewed. Median follow-up duration was 10.5 years. Competing-risks methodology determined time-related prevalence and associated factors for three mutually exclusive end states: death, valve reoperation, and survival without subsequent reoperation. Results: One hundred and ten children (age 15.6 ± 2.6 years, 80% females) underwent 123 valve replacements with biologic and bioprosthetic substitutes including 87 MVR and 36 AVR (13 had both). Underlying pathology was mainly rheumatic fever (91%). Thirty-nine patients (35%) had undergone a previous cardiac surgery. Most common mitral substitute was Hancock (73%) and homograft (8%); most common aortic substitute was homograft (41%) and Carpentier–Edwards (39%). Competing-risks analysis showed that 15 years after valve replacement, 16% of patients had died without subsequent reoperation, 66% underwent valve reoperations, and only 18% remained alive without further reoperation. Factors associated with increased reoperation risk included younger age at surgery (p = 0.005), AVR (p = 0.005), male gender (p = 0.02) and homograft use (p = 0.007) especially in the mitral position (p = 0.002). Fifteen-year freedom from endocarditis was 97% while freedom from bleeding and thrombo-embolic complications was 100%. Majority of patients (95%) were in NYHA functional classes I/II at last follow-up. Conclusion: While valve reoperation is inevitable following AVR and MVR with biologic and bioprosthetic substitutes; favorable results such as low valve-related morbidity rate, good long-term survival and functional status encourage their consideration as valid replacement alternatives in selected children especially females. Valve durability is higher in the mitral position and longevity of bioprosthetic valves is greater than that of homografts especially in the mitral position. Mitral valve replacement • Aortic valvereplacement • Rheumatic fever • Homograft • Pulmonary autograft • Bioprosthetic valve 33 34 http://www.iscs.org.ir/journals/vol.2/no.4/53/