Objective To evaluate the value of interphase fluorescence in situ hybridization(FISH) in the detection of acquired complete and partial deletion of chromosome 5(-5/5q-) in myelodysplastic syndromes(MDS). Methods Marrow cells from 48 MDS patients and 10 normal controls were studied by interphase FISH using SpectrumRed directly labelled DNA specific probe for 5q31, 200 to 300 cells were scored for each case and cells with a red hybridization signal6% were defined as -5/5q- positive. Results In 48 MDS patients, 13 were positive for interphase FISH,of whom, 7 were positive and 6 were negative for conventional cytogenetics(CC). The difference in the percentage of positive cells detected by the two methods was statistically significant(P0.05). Conclusion Interphase FISH is more sensitive than CC for the detection of -5/5q- in MDS.