The mistletoe lectins are major active components in the extrct of Viscum album var. coloratum. This study was performed to investigate the anti- skin cancer effect of Korean mistletoe extract intensified with mistletoe lectin (KI 2103S). B16F10 melanoma cells were allografted in C57BL/6 mice and F344 rats. The effect of KI 2103S on melanoma was measured by monitoring tumor index. The KI 2103S was injected intra-tumorally and tumor index was decreased in dose dependent manner.