Five eight week old dogs were inoculated orally and intranasally with cell culture origin canine parvovirus. Three dogs became depressed and anorectic and developed a mild (one dog) to severe diarrhea five days postinfection. The remaining dogs had subclinical infections but developed a lymphopenia followed by a transient lymphocytosis. The ill dogs developed mild (one dog) to severe neutropenia and a moderate lymphopenia. One died nine days postinfection. Recovery was associated with cessation of viral excretion and with lymphocytosis and antibody production. Two of three dogs challenged intragastrically developed mild clinical signs and a moderate panleukopenia four to eight days postinfection. The pathological changes of the experimental disease were very similar to that of spontaneous disease. Bone marrow changes included a severe granulocytic and mild erythroid depletion. The pathogenesis of canine parvovirus infection is discussed.