Ten groups each of five guinea pigs were inf ected by corynebacterium ovis through the fo llowing routs of infection: skin scarificati on, intradermal, subcutanous, intramuscular, per oss, intranasal, intraoccular,intra-vagi nal, intra-urethral, and per rectum. Corynea Bacterium ovis was pathogentic to gui nea pigs by all routes of infections. The pre imary lesions were related to the seat of entery and regional lymph nodes. They reflect the behaviour of corynea ovis as pyogenic and toxogenic microorganism. Microphages were the most predominating reacting cells. Macrophages were unsegnificantly present. Caseation of neutrophiles reflect direct cytotoxic effect. Indirect cytotoxic effect was manifested by vascular dammage inform of fibrincid dystrop hy and thrombosis. Generalization of toxins from primary lesions resulted in early and late toxaemia. Secondary metastatic lesions in the parenchymatous organs were related to vascular damage.