Cytogenetic analysis is important for the diagnosis, therapeutic approach and follow-up of malignant diseases. Specific chromosomal changes in leukemia are important prognostic tool. Translocation t (15;17) (q22;q11-12) is highly specific for M3 (promyelocytic) leukemia and has not been detected in any other malignancy so far. Case report: A man at age 59 years had clinical manifestations of M3 leukemia. Bone marrow showed significant hypercellularity accompanied by megaloblastic erythroid lineage, high number of dysplastic megakaryocytes, PAS negativity, POX negativity, AF negativity, and positive esterase. All findings were concordant with the diagnosis of promyelocytic leukemia AML-M3. Cytogenetic analysis performed by the standard direct technique from the bone marrow showed significant polyploidy and deletion 17 (q11-12) in all analyzed metaphases. This was unfavorable sign for M3 leukemia. The patient did not respond to AIDA protocol and expired shortly after the initiation of the therapy. It has been documented that during the translocation t (15;17) fusion of PM/RARA genes occurs increasing sensitivity of AML-M3 cells towards standardized ATRA (all-trans-retionic-acid) protocol. Sensitivity to ATRA is crucial since it leads to resolution of disseminated intravascular coagulation and promotes remission. Only patients with t (15; 17) respond favorably to ATRA protocol. In our patient, although the break point on the chromosome 17 was the same as in the specific translocation, fusion PM/RARA failed to occur, thus his response to treatment was poor. In conclusion, cytogenetic analysis in M3 leukemia is beneficial since it might help choice of the therapeutic protocol.