Introduction. The objective of the study was to determine the maximal inspiratory mouth pressure (PImax) of highly trained male and female athletes competing in endurance sports and of non-training students of both sexes. Analysis was conducted of the dependence of PImax levels on somatic indices and training experience. The reproducibility of the method for measuring PImax index was determined. Material and methods. The study examined a total of 234 training and non-training individuals (78 women and 156 men). The test subjects were measured for PImax, as well as inspiratory time, active time, passive time and diaphragm relaxation time. A group of 59 women and men (training and non-training) were tested a second time within 5-7 days of the first test to determine the reproducibility of the PImax measurements. Results and conclusion. The measurements were found to be highly reproducible (between the first and second tests no statistically significant differences were found, all spirometric indices included in the study were shown to demonstrate a significant correlation, and total error for all of the analyzed indexes was between 11.1 and 24.3%). Reference ranges for PImax were determined for women and men at different training levels. PImax was shown to have a positive dependence on somatic indices characterizing male and female body mass.