A 52-year-old male patient with chronic neutrophilic leukemia (CNL) with dysplastic features is described. He had a 2-year history of anemia followed by marked leukocytosis up to 57.5 x 10(9)/l with 88% segmented neutrophils. Bone marrow aspiration and biopsy showed hypercellular marrow with myeloid hyperplasia and 16% myeloblasts. There were also significant morphological abnormalities which included neutrophils with few granules, hypersegmented nucleus or Pelger-Heut anomaly, and micromegakaryocytes. Cytogenetic analysis disclosed a deletion of the long arm of chromosome 7 (7q-). He was diagnosed as having CNL with dysplastic features and was treated conservatively. However, leukemic transformation to acute myelogenous leukemia occurred within a year and he died 16 months after diagnosis. Neutrophilia is a feature not of myelodysplastic syndromes (MDS) but rather of myeloproliferative disorders such as CNL. However, this patient was considered to have MDS with increased proliferation and differentiation of neutrophilic lineage, because of marked myelodysplasia and poor prognosis.