The pulmonary blood volume (Q) can be measured by dye injection in the pulmonary artery (PA) and in the left atrium (LA) and by sampling in the brachial artery (double injection - single sampling method). We propose to replace the injection in the LA, for which a left heart catheterization is needed, by a pulmonary wedge injection (PW). No significant difference was found between the first and the second method in twenty-four measurements in six anesthetized and artificially ventilated dogs kept in steady hemodynamic state : QPW (1) equals 0.009 + 1.106 QLA (r equals 0.935). The results are independent of the capillary injection site. In man, the indirect validation was made by unilateral occlusion of a main pulmonary artery, allowing blood volume measurement of the occluded lung by two methods, one of them independent of the "capillary" injection. The results of both methods are comparable and highly correlated (r equals 0.86). The range of the values of pulmonary blood volume in sixteen normal supine subjects, at rest, was similar to that of other authors, whichever the technique they used (394 plus or minus 114 ml, 268 plus or minus 59 ml m-2). The reproducibility of the results was comparable. In five subjects, pulmonary blood volume did not change during a moderate muscular excerise in the supine position (57 watts). The pulmonary wedge injection in man can replace the LA injection of the double injection - single sampling method, without loss of precision nor effect on reproducibility.