Patients with gastric adenocarcinoma are most frequently diagnosed at an advanced stage. The disease has a marked propensity for loco-regional spread and will be the sole or major site of disease in up to 80% of patients. Various attempts at controlling loco-regional disease have not been successful. The selective lethal effect of supranormal temperatures on neoplastic cells and the additive or synergistic effect of combining chemotherapy has been well established in laboratory models and has provided the rationale for numerous clinical trials using hyperthermic isolated limb perfusion for advanced extremity melanoma or sarcoma. This Phase I study will evaluate the safety of escalating temperatures of continuous hyperthermic peritoneal perfusion (CHPP) with escalating doses of intraperitoneal Cisplatin (CDDP) in the treatment of patients with advanced peritoneal adenocarcinoma of gastrointestinal origin.