Some investigators claim that the viability of cryopreserved human valvular homograft is necessary for the duration of implanted homograft. In this preliminary study, the percentage of cycling cells in cryopreserved valvular homografts was evaluated with the use of monoclonal Ki-67 antibody. Three human aortic valves were harvested from multiorgan donors and cryopreserved. Sections of 5 microm in thickness were stained with monoclonal Ki-67 antibody. The proportion of endothelial cells with Ki-67 positive nuclei was 1.80 +/- 0.20%. No differences in distribution were observed from basal to marginal sites. Few fibroblasts showed Ki-67-immunopositivity (0.10 +/- 0.06%) while the Ki-67 immunostaining was 0.80 +/- 0.20% in myocytes. Our preliminary study shows that cryopreserved valvular homograft cells are not only viable but they also have the potential to replicate. These data can lead to the hypothesis that valvular cells could actively replicate even after implantation, permitting cellular renewal and regeneration of extracellular matrix's components.