The effect of physical exercise on erythrocyte 2,3-diphosphoglycerate (2,3-DPG) content was studied in eight trained speed canoeists aged 15-25 years. One-stage-4-min load on a paddling ergometer corresponding to a 1 km race was observed. During the test, the following cardiorespiratory parameters were recorded: V, VO2, VO2/kg, HR, VO2/HR, R. Blood lactate level and haematocrit were also determined. The average resting values of 2,3-DPG and haematocrit were statistically significant increased. After 6 months intense training there was a significant increase in 2,3-DPG, and the other parameters were also increased.