Background: With the rise in popularity and availability of simulators for the aircraft training of pilots, numerous side effects of that technology have been noted among their users. The symptoms of simulator sickness are similar to the symptoms of motion sickness. Dizziness, nausea, as well as spatial disorientation and a limited capacity for concentration may be observed. However, those symptoms depend on individual user’s predispositions. Material and Methods: The aim of the research was to assess the probability of occurrence of simulator sickness during exercises in virtual reality, and its impact on the effectiveness of training. Thirty two military and 16 civilian pilots of various types of aircraft took part in the research. For the subjective assessment of the psychophysical condition of the pilots, a questionnaire based on Simulator Sickness Questionnaire (SSQ) was used. Results: Four main factors that are associated with the prevalence of simulator sickness have been identified, i.e., age, a variety of missions, a type of aircraft and susceptibility to motion sickness. Conclusions: Due to the individual characteristics of each person, determining the risk of occurrence of simulator sickness seems to be difficult. However, there are some factors that increase the probability of getting sick, including cold, medications, lack of sleep and general fatigue. The lack of knowledge about simulator sickness among aircraft pilots appears rather alarming. When access to virtual reality is so wide, the possible ways of expanding the knowledge in this area should be considered, especially in order to obtain better results in simulator sessions. Med Pr. 2019;70(3):317–25