Background & objectives: The presence of t(15;17) or PML-RARα fusion transcript is the diagnostic hallmark of patients with acute promyelocytic leukaemia (APL). Cytogenetic (CG), fluorescent in situ hybridization (FISH) and reverse transcriptase-polymerase chain reaction (RT-PCR) are mainly the techniques used for detecting this abnormality. The objective of this study was to compare and assess the role of CG, FISH and RT-PCR in the diagnosis of APL. Methods: CG, FISH and RT-PCR analysis were performed in 29 patients with APL (28 M3, 1 M3v; 27 studied at diagnosis and 2 at relapse). Results: Karyotypes obtained in 25 patients revealed t(15;17) in 21 normal karyotype in 3 and trisomy 8 in 1 patient. In 26 patients FISH was positive for PML-RARα fusion in both interphase (IP) and metaphase, two were negative and one patient had no cells for FISH analysis. IP FISH confirmed the fusion of PML-RARα in all patients with t(15;17) detected by CG. RT-PCR was positive in the 22 patients analyzed (7 patients did not have RT-PCR). PCR was positive in the 3 patients with cytogenetically normal karyotypes and in one patient when karyotyping was a failure. CG detected 21 (72.4%) patients with t(15;17) of which additional chromosomal abnormalities were detected in 20 per cent of patients with successful karyotype. Interpretation & conclusion: FISH and RT-PCR were useful in detecting PML-RARα fusion in cytogenetically normal patients and those in when karyotyping was a failure and can be used in routine analysis for rapid confirmation of t(15;17) in patients with acute myeloid leukaemia.