Objective: The aim of this study was to evaluate the effects of lysozyme on the tumorigenicity of B-16V melanoma cells. Methods: After performing a series of molecular biology applications, including mRNA isolation, reverse transcriptase polymerase chain reaction, restriction digestions and ligations, recombinant pHM6 vector harboring mouse lysozyme gene (pHM6mLys) was constructed. B-16V melanoma cells were transfected with plasmid DNAs (pHM6 and pHM6mLys). Transfected cells (B-16VpHM6 and B16VpHM6mLys) were selected in media containing geneticin. B-16V, B-16VpHM6, and B-16VpHM6mLys cells were then injected subcutaneously (s.c.) to the three groups of C57BL/6 inbred mice (30 mice/group). These mice were examined every 3 days for s. c. tumor development over 41 days. The results were evaluated by using statistical methods. Results: Tumor formation was observed in all mice injected with B-16V and B-16VpHM6 cells in the first 8-12 days. However, tumor didn't develop in 16 of 30 of the mice injected with B-16VpHMmLys cells. Tumor-free animals (16 mice) in this group were reinjected with B-16V cells, and 9 of them died during the first 10 days of observation. Tumor development was not observed in the remaining 7 mice over 60 days of the experimental period. Results were statistically significant (p values <= 0.05). Conclusions: These findings indicate that lysozyme expressed by B-16VpHMmLys cells may suppress the tumorigenicity of these cells and may help development of protective immunity against B-16V melanoma cells.