Abstract: Fluorescence in situ hybridization (FISH) is a promising technique used in cytogenetic researches at the molecular level.In this paper,the current and potential uses of this technique in fishes are reviewed,with regards to such fields as gene localization,sex identification,chromosome variation,and interspecies hybridization.FISH has been successively applied into localization of rRNA gene in many kinds of fishes,which not only enriched the cytogenetic studies of fishes but also provided deep implication for chromosome evolution of fishes.Histones gene and some disease-related genes have also been localized in several fish species.Sex-specific FISH probes (including sex-related probes and sex-chromosome-related probes) have been obtained and put into sex identification of several fish species.Species-specific FISH probes have been used to examine chromosome elimination and interspecific hybrids in several kinds of fishes.In the same way,telomere repetitive sequences have been localized in several fish species and used to examine chromosome rearrangement.Centromere-specific probes and telomere-specific probes will be helpful in chromosome identification and sorting of fishes whose chromosomes are too small to be easily analyzed with traditional techniques.