The bone marrow aplasia is defined as a decrease in the production of the medullar cells lineages which are substituted by fat or a fibrous connective tissue, and its main causes are drug intoxication, toxins, hyperestrogenism, neoplasms, canine ehrlichiosis and canine parvovirus. The canine parvovirus type 2 shows tropism for cells in active mitosis and is able to replicate itself in the primary and secondary lymph tissue, besides cells from the intestinal endothelium crypt. A panleucopenia or apparent lymphopenia can be observed after the infection, so that the decrease of the in vivo cells is explained by the virus replication in the erythroid and myeloid progenitor cells or due to other indirect effects still unknown of the virus replication. An animal from the canine species, female, 10 months old, no defined breed was served in the Anhembi Morumbi Veterinary Hospital with history of epistaxis, hyporexia, emesis and moderate apathy for at least 5 months. It never went through vaccination or administration of antiparasitic treatment. In the physical examination the animal showed pale mucosa, epistaxis and petechiae located mainly in the abdomen. The laboratory tests showed panleucopenia characterized by nonregenerative anemia, leukopenia and a severe thrombocytopenia. The coagulation tests (coagulation time, prothrombin and partial activated thromboplastin time) showed results in the normality range and the canine ehrlichiosis serological tests obtained negative results. Subsequently, an aspiration cytology of the bone marrow was held, in which moderate hypoplasia of the erythrocytic, megakaryocytic and granulocytic series was observed, and also the absence of infectious and neoplastic agents, which indicated a bone marrow hypoplasia. Due to the fact that the dog had not been vaccinated, an investigation for serum antibodies against parvovirus was held through Immunofluorescence Assay (IFA) with a positive result with high title (1/320--positive titles considered > 1/20). The therapeutic protocol set was of antibiotic (enrofloxacin 5mg/kg/BID); immunosuppressive drugs (cyclosporine 10mg/kg/BID) and prednisone (2mg/kg/BID); bone marrow stimulators (erythropoietin 100U/kg/48h) and filgrastim (5mcg/kg/SID) and vitamin complexes, besides many blood components transfusions (erythrocytes and platelets concentrates). After 3 months of treatment there was no satisfactory improvement and a new bone marrow puncture was held, revealing a medullar aplasia with the absence of progenitor cells. Since that the animal had been stable due to blood transfusions, and died after 2 months. It is known that the canine parvovirus is present among the causes of medullar aplasia in dogs an unfavorable prognosis when it's diagnosed late.