Eimeria tenella-induced hemorrhage resulted in total blood losses of up to 10% of the body weight. Although packed cell volume was reduced 50%, neither plasma volume nor blood volume was significantly decreased, except briefly. The retention of lost blood in the ceca varied with the strain of E. tenella. Chicks infected with laboratory strain (L.S.) 24 passed most of the blood into the feces, whereas those infected with L.S. 49 retained most of the blood within the ceca.