SummaryThe purpose of the present study was to determine the hydraulic conductance (Lp) of human and canine pericardium and evaluate the influence of several factors on Lp. The Lp of canine and human pericardium was 9.6 • 10 -5 and 4.5 • 10 -5 ml/ min/cm2/crnH20 respectively. There was no relationship between Lp and membrane thickness within each species but membrane thickness differences between species may account for some of difference in Lp. Hypertonic media cause Lp to increase. Lp was independent of hydraulic pressure over the range from 6 to 15 cm H20. The magnitude of Lp suggest that the parietal pericardium is a potentially important route for removal of pericardial fluid especially in cardiac tamponade.