OBJECTIVE Changes in blood flow distribution are important for heat dispersion and for supportive therapeutic strategies such as simultaneous whole body hyperthermia (WBH) and administration of chemotherapy. The aim of this clinical study was to determine changes in hepatic blood flow during WBH for the treatment of metastatic cancer. METHODS This observational clinical study was part of a phase I/II feasibility study of WBH. WBH was induced using a radiant heat device. Hepatic blood flow was estimated using indocyanine green clearance measurements. The plasma disappearance rate of indocyanine green (PDR-ICG) was recorded in percent/min. We used an invasive thermo-dye-dilution technique to estimate hepatic blood flow, cardiac output, and volume status. Mean arterial blood pressure was also measured invasively. To determine the effects of hyperthermia the measurements were performed at defined temperature points. RESULTS In 10 of 22 treatments the PDR-ICG fell below normal values during hyperthermia, which represented a significant fall in hepatic blood flow. Cardiac output, volume status, and mean arterial blood pressure did not differ between patients whose liver blood flow was reduced and those whose liver blood flow remained unchanged. CONCLUSIONS We observed distinct reductions in hepatic blood flow during WBH, which suggested a significant redistribution of blood flow away from the core during WBH. This was not mirrored by global circulatory parameters.