Twenty-eight patients with advanced upper-abdominal malignancy were treated at the University of Utah on a pilot protocol involving regional hyperthermia (HT) produced by the BSD-1000 HT system and the annular phased array applicator (AA), usually driven at 60 MHz. Eighty-two percent of the patients had widespread metastatic disease, and the mean tumor burden was 2,900 cc. Seventy-nine percent of the patients received concurrent radiotherapy. Acute toxicity consisted primarily of pain within the AA aperture (43%), systemic stress (43%), and nausea or vomiting (29%). Systemic stress was the most frequent power-limiting factor (46%). There were two treatment-related complications: sciatic neuritis from intramuscular injection (one) and pleural effusion from thermometry probe placement (one). Detailed thermal mapping and thermal dosimetry were performed on 26 patients. The mean thermal dosimetry parameters were quite low. Concurrent radiation doses were also quite low (mean, 1,500 rad) to avoid toxicity of sensitive organ systems within the abdomen. The objective response rate was only 18%, all partial, but 43% of the patients achieved effective symptomatic palliation. The five objective responders did survive significantly (P = .02) longer than the 23 nonresponders.