Among the various types of human interferons, human interferon-beta (HuIFNbeta) has the strongest anti-proliferative activity against human melanoma cell lines. Therefore, we investigated the growth inhibitory effect of a cationic liposome containing the HuIFNbeta gene on human melanoma cell lines in vitro and in vivo. After transfection with liposomes containing the HuIFN-beta gene, human melanoma cell lines produced HuIFNbeta in the culture medium at levels ranging from 67 to 3.8 IU/ml on day 6, and growth of the cells was inhibited by 71-92%. Moreover, six injections of liposomes containing the HuIFNbeta gene completely eradicated human melanoma nodules transplanted onto the backs of nude mice 40 days after the first injection. Histological analysis of the injected nodules revealed that the HuIFNbeta gene transfection induced apoptosis of the human melanoma cells. These data suggest that transfection of the HuIFNbeta gene using cationic liposomes is a promising candidate for gene therapy of human melanoma.