Chromosome rearrangement induced by bleomycin were identified by fluorescence in situ hybridization with probe for chromosome 4. The frequency of color junctions, translocations, dicentric and acenttic fragments increased with bleomycin dose. Different types of balanced translocation and dicentric were scored and compared. The frequency of cells exhibiting multiple aberration was higher compared to that of cells exposed to Gamma radiation suggesting that effect of bleomycin might be similar to that of high LET radiation.