This phase I-II study investigated the feasibility of external deep loco-regional hyperthermia in localized primarily operable carcinoma of the thoracic oesophagus and gastro-oesophageal junction. Toxicity when combining neo-adjuvant hyperthermia with concurrent chemotherapy (CDDP and etoposide) was evaluated. Hyperthermia was given with a four antenna array, operating at 70 MHz arranged around the thorax. Temperatures were monitored rectally, intra-oesophageal at tumour level and intramuscular near the spine. In four steps, a thermal dose escalation was performed from 15-60 min of heating to 41 degrees C with two patients in each step. The combined treatment courses were repeated every 3 weeks for a maximum of four courses. From January 1999-February 2002, 31 patients were included. Pre-treatment tumour stage mainly consisted of T3N1 (stage III) tumours, with a mean length of 6 cm. The maximum tumour temperature failed to reach at least 41 degrees C in five patients during the test session of hyperthermia alone. Combined hyperthermia and chemotherapy was given 55 times in 26 patients. The amplitude was set at a ratio between top:bottom:left:right = 1:3:3:3, with a power range of 800-1000 W. Thermal data showed that is was technically feasible to heat the oesophagus; the median results were T(90) = 39.3 degrees C, T(50) = 40 degrees C, T(10) = 40.7 degrees C and a median T(max) = 41.9 degrees C. In more distally located tumours higher temperatures were reached. In one patient, a transient grade 2 sensory neuropathy was seen. Further toxicity was mainly of haematological origin. Blisters or fat necrosis were not observed. Twenty-two patients underwent oesophageal-cardia resection with gastric tube reconstruction. There was no report of complications in the post-operative phase, which could be contributed to either the prior chemotherapy or the hyperthermia.