The experimental manipulation of protooncogenes and their gene products is a valuable research tool for the study of human neoplasia. In this study, the recently identified human cervical cancer protooncogene (HccR-2) was expressed in transgenic mice under the control of the tetracycline regulatory system. Mice expressing the HccR-2 transgene showed an altered myeloid development characterized by an increased percentage of mature and band-form neutrophils in the peripheral blood, liver and spleen. This phenotype is similar to human chronic neutrophilic leukemia (CNL) in many ways, which is a rare chronic myeloproliferative disorder (CMD) that presents as a sustained leukocytosis of mature neutrophils with a few or no circulating immature granulocytes, an absence of peripheral blood monocytosis, basophilia, or eosinophilia, and an infiltration of neutrophils into the liver, spleen and kidney. Thus, the HccR-2 transgenic mouse model is imperative not only for investigating the biological properties of the HccR-2 protooncogene in vivo, but also for analyzing the mechanisms involved in the progression of CNL.