RAR-Beta receptor is expressed and up-regulated in response to ATRA in a good proportion of patients with AML. A considerable variability was noticed regarding the basal expression levels and the amplitude of up-regulation. FAB subtypes and CD34 expression may influence the response to ATRA but other contributing factors should be considered. Up-regulation of RAR- Beta receptor expression in AML was not associated with granulocytic maturation. Since the retinoid protocols for non-M3 AML patients have drawn attention in the past years, the ability to express and up-regulate RAR- Beta receptor in AML leukemic cells may be useful as predictive test during treatment with retinoids especially with the availability of real time PCR as a sensitive, specific, rapid and quantitative assay for RAR- Beta receptor expression.