133Xenon washout from the femora of 5 anesthetized rabbits was recorded during short hyperbaric exposures (3 atm abs). Equipment tests showed that the scintillation counter was heat sensitive. The recorded count rate from a constant source of 133xenon decreased during compression (temperature rose 5 degrees C) and increased during decompression (temperature fell 5 degrees C). When the scintillation counter was thermally insulated, the rate of xenon washout from the femur remained unchanged in all rabbits during these hyperbaric exposures. The conclusion is that the rate of xenon washout from the femur is not affected by changes in ambient pressure. As most scintillation counters are heat sensitive, it is possible that the previous report of such changes was erroneous and caused by heat sensitivity of the recording equipment.