To explore the value of multiplex fluorescence in situ hybridization (M-FISH) technique in the detection of the complex chromosomal aberrations (CCAs) in myelodysplastic syndromes (MDS).M-FISH was used in ten MDS patients with R-banding CCAs to refine the complex chromosomal rearrangements, the constitute of marker chromosomes, and to identify the cryptic translocations.Thirty-seven kinds of structural rearrangements were detected by M-FISH including insertion, deletion, translocation and derivative chromosomes, among which 34 kinds were unbalanced rearrangements, and 3 were balanced rearrangements including t(6;22) (q21; q12), t(9; 19) (q13; p13) and t(3;5) (?; ?).