Abstract: The effect of therapy, tissue distribution and stability are studied in nude mice bearing human colon tumor after injections of 188Re labelled stannic sulfur suspension. The tissues are observed with electric microscope. The results show that 188Re labelled stannic sulfur suspension is stabilized in the tumor and its inhibitive effects on human colon tumor cells are obvious. 188Re labelled stannic sulfur suspension is a potential radiopharmaceuticals for therapy of human tumor.