A 52 year old male presenting chronic myeloid leukemia (CML) Philadelphia chromosome positive (Ph) four years after the diagnosis of a non Hodgkin's lymphoma is described. The patient had received high total doses of alkylating drugs (cyclophosphamide and chlorambucil) as part of chemotherapy treatment for a diffuse mixed lymphoma. At four years of diagnosis of the lymphoma the appearance of hepatosplenomegaly, leukocytosis with myeloma and basophilia and thrombocytosis were observed. These alterations augmented progressively until a cytogenetic study of the bone marrow two years late established the diagnosis of CML upon demonstrating the presence of the Ph chromosome with no other karyotypic anomalies being observed. The explorations carried out at that time confirmed that the lymphoma continued to be in remission. The CML initially responded to treatment with busulphan. However, following a year and a half the disease evolved to a phase of acceleration and the patient died a few weeks later due to pneumonia with no signs indicative of lymphoma activity having been detected since the diagnosis of the CML.