A patient with chronic myelocytic leukaemia (CML) and a new complex Philadelphia chromosome (Ph') translocation, t (10; 14; 22), is described. This three way Ph' translocation not involving chromosome 9 was present in the majority of the bone marrow cells, as well as in a great proportion of metaphases from phytohaemagglutinin (PHA) stimulated peripheral blood cultures. The possibility that the Ph' translocation was present also in lymphocytes is discussed and at this regard the involvement of chromosome 14 is of interest considering the documented non random involvement of chromosome 14 in lymphoid malignancies.