Seven patients with advanced cancer underwent whole-body hyperthermia using a nylon and vinyl mesh, water-perfused suit. Treatments were given at 41.8 degrees C for 4 hours. Five patients received concomitant cyclophosphamide with hyperthermia. Compared to baseline (37 degrees C) conditions, there was a significant rise in pulse rate (P less than 0.001), a fall in diastolic pressure (P less than 0.02), and an increase in respiratory rate (P less than 0.001). Toxic effects included fatigue, extremity edema, diarrhea, nausea and vomiting, and respiratory depression in a patient with cerebral metastases. Compared to baseline values, there was a significant increase in serum glucose (P less than 0.02) and decreases in serum calcium (P less than 0.01) and phosphorus (P less than 0.01). Significant elevations in serum LDH and SGOT values occurred 24 hours following hyperthermia, suggesting hepatic sensitivity to heat. The methods used to induce whole-body hyperthermia, as described in this paper, are feasible, permit relatively easy access to the patient, and are potentially applicable in diverse hospital settings such as intensive care units, radiation therapy areas, and conventional rooms. The physiologic alterations that were observed and the toxic effects that were documented indicate that careful monitoring of patients is necessary.