The physical fitness of the young Finnish men called up to the military service has gradually declined during the last three decades. During the 6-month military service conscripts undergo basic military and physical exercise training which should improve their fitness. The objective of this study was to investigate cardiorespiratory and muscular performance of the conscripts during their last and longest (12 days) field exercise of the military service in the winter conditions. Hypothesis is that if excessive fatigue exists during the prolonged training, it should be seen as reduced performance capacity. Subjects were 21 male jaegers. Each subject participated three times in maximal muscle performance and cardiorespiratory tests: three days before (T1), at the 5th day (T2) and at the 12th day (T3) of the field training. Maximal isometric leg extension (LE), static jump (SJ), counter movement jump (CMJ) and wrist rotation (WR) were tested. SJ, CMJ and WR were also measured every day in the field. Mean maximal VO₂ was maintained but maximal heart rate significantly decreased in T3 compared to T1. No significant changes occurred in SJ, CMJ, LE and WR in T2 or T3. Daily measurements after strenuous physical activity showed significant but temporary decrement in muscle performance. Minor changes in cardiorespiratory and neuromuscular performance suggest that the partly motorized infantry troops were capable to perform their field training without cumulative fatigue. The results reflect that the physical training during the military service is adequate to elevate the cardiorespiratory and muscular performance to the level which is sufficient in order to endure prolonged field exercise in infantry troops.