To evaluate the effectiveness of serotherapy for canine parvovirus (CPV) infection, immune serum was injected intravenously into dogs which had been infected experimentally with CPV or which showed clinical signs of CPV infection under field conditions. In experimentally CPV-inoculated group, serum-injected dogs showed mild clinical signs of the disease after serum treatment and all the dogs recovered, whereas non-serum-injected dogs showed severe clinical signs and half of the dogs died. In the field cases, many dogs recovered rapidly from the disease after the serum treatment. These results indicated the usefulness and effectiveness of the serotherapy for CPV infection in dogs.