Galectin-3, a β-galactoside-binding lectin, is localised within various parts of the cell and outside of it, expressed in multiple tissues and participates in various processes within the organism. Galectin-3 has recently been recognized as a biomarker of certain pathological states. The results of the few studies done on the effect of physical activity on plasma concentrations of galectin-3 are not in unison. In this study, the effect of high-intesity interval training, organised as repeated sprint training with a progressive increase in intesity in duration of six weeks, has been investigated. The study subjects were young healthy males. The blood samples were taken at three different time points: a – before the start of the experimental protocol, b – immediately after the penultimate and most intense training session and c – 1 month after the end of the experimental protocol. Galectin-3 concentrations were measured by a „sandwich“ ELISA method, using a commercially available Quantikine® ELISA Human Galectin-3 Immunoassay kit. The statistical data analysis was done by a two-way analysis of variance in GraphPad Prism 9.0.0. In none of the three examined time points, intense exercise did not cause statistically significant differences in the plasma concentration of galectin-3 between the experimental and control groups. In both groups, a similar pattern of reduction in galectin-3 concentration was observed, especially in the last measurement point (1 month after the end of the protocol) compared to the first (before the start of the protocol). The cause of such an outcome in this research is unknown, however, given that both the control and experimental groups were students of the Faculty of Kinesiology and that during the investigation everyone was allowed to exercise as part of their studies, it is possible that this exercise, which could be classified as moderate to intense, alone was sufficient to achieve the observed effect.