Otherwise healthy, participated in a strenuous physical exercise. DI measurements several hours before the exercise were consistent with extreme heat burden; however, during the exercise . DI measurements were within normal limits. Just before completing the training, he complained of shortness of breath and shortly later appeared disoriented. Initial rectal temperature was 39.6 after EHS diagnosis, he was treated by undressing him, pouring large amounts of water over him, and Intravenous fluids because of suspected additional dehydration and rushed to a nearby ED. On arrival at the ED, he regained full consciousness. Remeasured rectal temperature and complete blood workup were normal. He was discharged later that day. An HTT performed 6 weeks later was normal, and he returned to active service a few months later because of technical difficulties, but he was fit for service earlier.