The clinical course of chronic myelomonocytic leukemia (CMML) is extremely variable, and disease progression can occur at any time from diagnosis. Median survival is about 20 months. About 20% of patients develop acute myeloid leukaemia (AML). Multivariate analyses performed by several groups showed that elevated medullary blast count, low haemoglobin, elevated serum lactate dehydrogenase (LDH), and perhaps an increased lymphocyte count, are the most important independent prognostic parameters, whereas karyotype analysis was not consistently shown to yield additional prognostic information. Applying different scoring systems to 288 CMML patients included in the Düsseldorf MDS Registry, we found that the International Prognostic Scoring System (IPSS) was not useful for defining risk groups in CMML, while the Spanish Score, the modified Bournemouth Score, the Düsseldorf Score, and probably the MDAP Score, identified patient groups differing significantly in survival. These scores should therefore be employed for clinical decision making and for risk stratification in the context of clinical trials.