In healthy subjects the pulmonary artery pressure was measured during exercise tests with the aid of the flow guided catheterisation. The work load was determined on bicycle ergometer in recumbent position in form of a multistage exercise test with relative steady state periods till exhaustion was reached. In this way, during the highest work load (200 Watt) the systolic pulmonary artery pressure was 33.9 +/- 5.5 mm Hg, the diastolic pressure 17.5 +/- 3.6 mm Hg and the pulmonary mean pressure 24.7 +/- 4.0 mm Hg. The factors influencing the pulmonary artery pressure during work are discussed.