In 17 healthy males pulmonary blood flow distribution (PBFD), pulmonary artery pressure (PAP), wedge pressure (Pw), and cardiac output were measured at different lung volumes and body positions. The PBFD became more even and PAP increased at RV in the sitting position as compared to at FRC. PAP also increased at TLC, but PBFD became more uneven.In the lateral position the increased PAP at RV caused only a minor change in PBFD. In both erect and lateral position at RV the Pw close to the diaphragm increased more than did PAP.