v-abl, the oncogene transduced by Abelson murine leukemia virus, was first characterized by its ability to transform lymphoid cells. bcr-abl, the oncogene formed by a t(9;22) translocation thought to occur in human hematopoietic stem cells, is detectable in almost all cases of chronic myelogenous leukemia (CML), a malignancy of granulocytic cells. bcr-abl also causes a CML-like syndrome in mice whose bone-marrow cells are infected with a retrovirus transducing the gene. More recent reports have suggested that v-abl can, however, cause a disease similar to CML. We demonstrate here that v-abl, when transduced in a helper virus-containing system, causes disease similar to, but distinct from, the CML-like syndrome induced by bcr-abl. Animals whose bone marrow has been infected by v-abl virus develop modest splenomegaly, marked granulocytosis, and malignant disease of several hematopoietic cell types. Unlike animals with CML-like disease resulting from bcr-abl, the polymorphonuclear leukocytes from animals infected with a v-abl construct do not contain the v-abl provirus at a significant frequency. Histopathologic analysis also shows significant differences between the diseases caused by v-abl and bcr-abl.