Karyotyping is important for diagnosis and prognosis of myelodysplastic syndrome (MDS). Using fluorescence in situ hybridization (FISH) either mitotic or interphase cells can be analyzed and a higher number of cells can be screened. This study evaluated the effectiveness of FISH in detecting the most common chromosomal abnormalities [−5/del 5q/−7/+8/del 11q23 and −Y] in 40 patients with MDS. Karyotype detected abnormalities in 35.2% of the patients and FISH in 35%, while some abnormalities remained undetected by each approach but the association of both methods increased the detection rate up to 40%. [Copyright &y& Elsevier]