Abstract: The present invention relates generally to compositions useful in therapies involving the selective destruction of tumor cells in vivo. In particular, this invention relates to a conjugate which comprises a target recognition segment and an active cytotoxic segment. The target recognition segment comprises a receptor specific to NK cells, wherein the receptor binds to a cellular ligand expressed on the surface of a tumor cell, and the active segment comprises an agent capable of exerting a cytotoxic effect on the tumor cell. The target recognition segment derived form the natural killer receptor NKp30 has been found to be particularly effective in vivo.