Based on clinical and pathological findings, chronic myelomonocytic leukemia (CMML) differs from other myeloproliferative/myelodysplastic disorders by its hallmark, monocytosis. It is unknown whether the presence of monocytosis and the diagnosis of CMML carry a prognostic significance. The present study aimed to determine whether the survival of patients with CMML differs from that of patients with BCR/ABL-negative CML or Ph(1-), BCR/ABL-unknown CML, once other potentially prognostic variables have been accounted for. The records of 485 patients with myeloproliferative/myelodysplastic disorders [CMML, n = 304; BCR/ABL-negative CML, n = 107; Ph(1-), BCR/ABL unknown, n = 74] were analysed. Of the covariates found to be significantly (P < 0.01) associated with survival in univariate and multivariate analyses, the following remained predictive and adversely associated with survival, after accounting for the influence of other covariates: increasing age, white blood cell count, platelets, bone marrow blasts and cellularity, decreasing hemoglobin, abnormal karyotype, and diagnosis of CMML. The diagnosis of CMML is prognostically significant and independently associated with a shorter survival and a higher risk of death than BCR/ABL-negative CML or Ph(1-) BCR/ABL-unknown CML.