A 0.75% Na citrate soln. in 0.85% NaCl under pressure is used to perfuse veins where schistosomes lodge. Tubing offshoots of a main line from the reservoir allow for perfusion of several animals simultaneously. For perfusion of mesenteric vessels, a hypodermic needle or a glass cannula attached to the pressure line is inserted into the aorta and the fluid plus worms wash out through the portal vein. Before perfusion of the liver its main vessels are doubly ligated, severed, and the liver removed. A pressure line as above is inserted into the hepatic vein and fluid plus worms escape through a cut in the portal vein. Perfusates from different regions are collected separately and the worms are recovered by sedimentation.