The aim was to determine relations of physical fitness and high-altitude sickness symptoms and drug usage in nonathletes visiting hypoxic environment. Subjects, 17 males (age 47.8 ±10.65), participated in 26-days trek (2500-6476m). Before the trip an all-out treadmill test was performed (maximal speed/ grade and estimated VO2max recorded). At every new sleeping altitude, the information about drug consumption and altitude sickness symptoms was noted. There were 7 subjects without symptoms. Others had headaches, insomnia and breathing distress. The used drugs were paracetamol, propyphenazone caffeine mixture, ibuprofen and aspirin. There were significant correlations between the occurrence of the symptoms and time on the treadmill (-0.504), achieved speed (-0.601) and grade of treadmill (-0.601), while no correlations between the physical fitness parameters and drug usage was confirmed. Then the subjects were divided in 2 groups according to VO2max (age adjusted). The age and the BMI of both groups were not significantly different (p=0.576 and 0.758, respectively). The Mann Whitney-U test showed the differences in both, the altitude sickness symptoms and in drug usage. The group with better estimated aerobic capacity had significantly less symptoms (Z=2.44; p=0.012) and consumed expectedly less drugs (Z=2.08; p=0.030). Altogether, the presence of the high-altitude sickness symptoms was not high apart from the expected tiredness. The level of physical fitness seems to be related to lower chance of highaltitude sickness, but it is not a guarantee to avoid it. Still an improvement in aerobic capacity before the ascent should still be considered.