OBJECTIVE To clarify apparently conflicting reports on the hemodynamic effects of the pneumatic antishock garment (PASG). METHODS Ten anesthetized dogs with hemorrhagic hypotension had hemodynamics measured without PASG inflation (group 1) and were compared with ten dogs with PASG inflation (group 2). RESULTS Baseline and immediate posthemorrhage data were similar in both groups. Group 1 maintained a carotid artery pressure of 85 +/- 9 mm Hg while group 2, by design, maintained baseline CP at 119 +/- 12 mm Hg. After PASG inflation, carotid artery flow increased by 50%, and femoral artery flow decreased tenfold. There was an immediate but transient increase (2.4 +/- 0.1 to 2.7 +/- 0.1 L/min, P less than .05) and a later decrease in cardiac output to 1.9 +/- 0.9 L/min and an increased pulmonary artery wedge pressure and central venous pressure over one hour. Saline (342 +/- 12 mL) reversed the decreased cardiac output without changing pulmonary artery wedge pressure or central venous pressure. CONCLUSIONS PASG inflation, therefore, not only increases venous return and cardiac output initially by compressive venous emptying but also decreases venous return and cardiac output later by further venous compression without cardiac decompensation. Thus, apparently conflicting data are explained by the timing and interpretation of the raw hemodynamic measurements.