The lack of evidence for the tissue-factor dependent activation of the coagulation system and the release of thrombin on one hand, and a decreased concentration of factor XII after short term air, saturated air and heliox exposures, as well as an increased concentration of the plasmin-antiplasmin complex (PAP) after short dives indicate that diving and decompression possibly affect fibrinolysis. The aim of our research was to verify the assumption that diving and decompression activate the system of fibrinolysis and the clarification of the pathomechanism of this activation.The study involved 50 healthy volunteers who were subjected to short-term, air hyperbaric exposures at 400 kPa and 700 kPa, which correspond to 30m and 60m dives. Decompression was applied in accordance with Naval tables of decompression. Before hyperbaric exposition and after decompression the following factors were determined: activity of factor XII, concentration and activity of t-PA, concentration and activity of PAI-1, concentration of alpha2- antiplasmin, concentration of PAP, concentration of neutrophil elastase.The following observations have been made: a statistically significant increase in the factor XII activity, increase in the PAP complex concentration and a simultaneous significant decline in the α2-AP activity. No measurable t-PA activity or significant changes in t-PA concentration have been observed. In addition, a statistically significant decline in both the activity and concentration of PAI-1 has been observed, which was more pronounced after the expositions that corresponded to 60 m dives. The concentrations of granulocyte elastase did not differ significantly before and after decompression.Conclusions: People qualified for diving should have the following risk factors examined: risk factors of increased fibrynolytic activity - haemostasis abnormalities that increase the risk of haemorrhage, possibility of parietal blood clots/thrombi.