We investigated the effects of Oak smoke flavoring (OSF, Holyessing) on the growth of DU145 and PC-3 human prostate carcinoma cells. OSF treatment resulted in a concentration-dependent growth inhibition in both DU145 and PC3 cell lines. The anti-proliferative effect of OSF treatment was associated with the induction of apoptotic cell death which was confirmed by morphological change such as membrane shrinking, rounding up and chromatin condensation in DU145 and PC-3 cells. DNA flow cytometry analysis confirmed that OSF treatment increased population of apoptotic sub-G1 phase. Furthermore, we observed an increase of pro-apoptotic protein Bax expression and a decrease of anti-apoptotic protein Bcl-2 by OSF treatment in a dose-dependent manner. OSF also induced a proteolytic cleavage of specific target proteins such as poly(ADP-ribose) polymerase (PARP) and β-catenin proteins. The present results indicated that OSF-induced inhibition of human prostate carcinoma cell proliferation is associated with the induction of apoptosis.