The retinoic acid receptor alpha (RAR alpha) protein plays a central role in myeloid differentiation, and chromosomal translocations disrupting the RAR alpha gene are implicated in the development of acute myeloid leukaemia (AML). To identify haemopoietic malignant disorders which may also be linked to RAR alpha abnormalities, Southern blot analysis was performed in DNA from 153 patients with haematological malignancies other than AML FAB type M3 using RAR alpha cDNA probes. Alterations of RAR alpha were detected in 1/42 myelodysplastic syndromes (MDS), 2/24 AML, 3/47 B-chronic lymphocytic leukaemias (B-CLL), 0/40 lymphomas and 0/60 normal individuals. These data strongly suggest that alterations of RAR alpha might predispose for myeloid and lymphoid disorders.