The present invention relates to an in vitro method of diagnosing chronic myelomonocytic leukemia (CMML) in a subject, said method comprising the steps of: a) Detecting a monocyte population in a biological sample from said subject; b) Quantifying the CD14+/CD16- monocytes in said biological sample; c) Comparing the value of step b) to a reference value; and d) Diagnosing CMML based on said comparison. Preferably, said detecting step a) is performed by an exclusion gating strategy by flow cytometry.
