The aim of this study was to investigate the impact on several forms of memory and metabolism of a 5-day combat course including heavy and continuous physical activities and sleep deprivation. Mnemonic performance and biochemical parameters of 21 male soldiers were examined before and at the end of the course. Our results showed that short-term memory (memory span, visual memory, audiovisual association) and long-term memory were significantly impaired, whereas short-term spatial memory and planning tasks were spared. Parallel biochemical analysis showed an adaptation of energy metabolism. The observed decrease in glycaemia may be partly responsible for the long-term memory impairment, whereas the decreases in plasma cholinesterases and choline may be involved in the short-term memory deterioration. However, there are also many other reasons for the observed memory changes, one of them being chronic sleep deprivation.