A patient with chronic myelogenous leukemia (CML) associated with pure red cell aplasia (PRCA) is reported. The occurrence of PRCA has been described previously in sporadic cases of Philadelphia chromosome (Ph) positive CML. In this patient, however, the Ph-chromosome was not detected; cytogenetic analysis revealed a t(12;14)(q23;p11) as the sole abnormality. Molecular studies by Southern and PCR analyses showed the rearrangement of the BCR and ABL sequences and expression of the chimeric bcr/abl mRNA, thus confirming the diagnosis of CML. To our knowledge, this is the first report on a case of PRCA associated with Ph negative CML at diagnosis. The possible connection between CML and PRCA is discussed.