BACKGROUND: Heat stroke is a thermal insult to the cerebral thermo-regulatory system that controls heat production and heat dissipation. Heat stroke occurs in all age groups and in different parts of the world. In the Korean army heat stroke can occur during marching or any other military training. This study was intended to reveal the pattern of neurological manifestations and brain images of heat stroke. METHODS: All patients who were transferred to one army hospital from March 2000 to September 2002 were included in this study and their neurological manifestations were recorded. A brain MRI was taken in 13 patients. PET images were taken in 6 patients. RESULTS: A total of nineteen patients were included in the study. The mean age was 20.2 (19~23) years. In the acute stage, all patients showed altered mentality and 11 patients showed seizure. During the subacute to chronic stage, the patients showed various neurological statuses ranging from normal to severe neurologic deficits such as abulia, cerebellar ataxia and so on. Brain MRI also showed various findings from normal to severe cerebellar atrophy. In one patient who showed persistent severe cerebellar dysfunction, the MRI showed progressive cerebellar atrophy. A PET image showed cerebellar hypometabolism in 5 patients and frontal hypometabolism in one patient. CONCLUSIONS: Heat stroke can cause various neurological deficits. Brain images can also vary. In the acute stage, the MRI may not correlate with clinical findings and may need a follow-up study. Additionally, a PET may explain neurological findings better in some cases.