This study explored the efficacy of Fa fraction of Tricholoma giganteum against Ehrlich's ascites carcinoma (EAC). Mechanisms of apoptogenic effect of the fraction were delineated. The flow cytometric analysis of EAC cells, showed an increase in number of cells in sub-G0/G1 population and reduction in the G2/M phase due to the treatment thus suggesting apoptosis. The induction of apoptosis has also been confirmed by nuclear staining that demonstrated distinctive morphological features of apoptosis. Our data also revealed an increase in the expression of pro-apoptotic protein p53 in EAC and induced factors contributing to apoptosis. Pro-apoptotic gene Bax was up-regulated during p53-mediated apoptosis. No significant change in the expression of anti-apoptotic protein Bcl-2 was observed ensuing in decrease of the Bcl-2/Bax ratio. p53-mediated growth arrest involves p21 as a major effecter, which interestingly showed moderate elevation. All these observations indicate that Fa fraction of T. giganteum induces apoptogenic signal in EAC. © 2012 Springer-Verlag.