It has recently been shown that cannabinoids induce growth inhibition and apoptosis in different tumour cell lines. In the current study, the effects of WIN 55,212-2 (WIN), a synthetic and potent cannabinoid receptor agonist, are investigated in hepatoma HepG2 cells and a possible signal transduction pathway is proposed. In these cells, WIN induces a clear apoptotic effect which was accompanied by up-regulation of the death-signalling factors Bax, Bcl-X(S), t-Bid and down-regulation of the survival factors survivin, phospho-AKT, Hsp72 and Bcl-2. Moreover, WIN-induced apoptosis is associated with JNK/p38 MAPK pathway activation and mitochondrial depolarisation demonstrated by a cytofluorimetric assay. The results also show that in HepG2 cells WIN markedly increases the level of the transcription factor PPARgamma in a dose- and time-dependent manner. The addition of the PPARgamma antagonists GW9662 and T0070907 significantly reduces the effects of the drug on both cell viability and the levels of survivin, phospho-AKT and phospho-BAD, suggesting that PPARgamma plays a key role in WIN-induced apoptosis. Altogether, the results seem to indicate a potential therapeutic role of WIN in hepatic cancer treatment.