DSD was studied for its prophylactic effect against peritoneal carcinomatosis using B-16 melanoma cell line. In in vitro examinations, incubation in medium containing 0.2% DSD significantly inhibited B-16 melanoma cells from adhering both to the plastic wall and the injured peritoneum, as compared to incubation in normal medium. Upon in vivo examination, intraperitoneal administration of 0.2% of DSD (1 ml/mouse) diminished the cancer cell number implanted into the injured peritoneum more than intraperitoneal administration of DSD-free medium.