Th effect.ofexperimental Babesia bigemina infection was studied in splenectomised and nonsplenectomised cow and buffalo claves. Pathological changes were found in the brain, lungs, heart, kidneys, lymph nodes, and spleen in nonsplenectomised animals). The post-mortem and histopathological pictures were that of anoxia and haemolysis. The course of the disease was more acute in cow calvesthan buffa'o claves : as indicated by the severity of the degene rative changes, degree of damag, to blood vessels, and pronounced haemolysis. Buffalo calves survived the d.sease longer period than cow calves, Also the severity of the mentioned indices indicated that splenectomy breaks the animal resistance. Hyperplasia of tht lymph follicales may be more or less of reactive paure to Babesia infection as to be a compensation to splenc ctomy, as found in the control animals,