Iso-suillin, a natural product isolated from Suillus luteus, has been shown to inhibit the growth of somecancer cell lines. However, the molecular mechanisms of action of this compound are poorly understood. Thepurpose of this study was to investigate how iso-suillin inhibits proliferation and induces apoptosis in a humanhepatoma cell line (SMMC-7721). We demonstrated the effects of iso-suillin on cell proliferation and apoptosisin SMMC-7721 cells, with no apparent toxicity in normal human lymphocytes, using colony formation assaysand 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) analysis. Western blotting was usedto examine the expression of G1 phase-regulated and apoptosis-associated protein levels in iso-suillin treatedSMMC-7721 cells. The results indicated that iso-suillin significantly decreased viability, induced G1 phase arrestand triggered apoptosis in SMMC-7721cells. Taken together, these results suggest the potential of iso-suillin asa candidate for liver cancer treatment.