Abstract: In this paper,we report on the cytogenetic detection of a triploid of Ctenophryngodon idellus by restriction endonuclease digestion and conventional banding techniques.Restriction enzymes Hae Ⅲ,Alu Ⅰ (recognizing four base sequences respectively) and Hind Ⅲ (recognizing a six base sequence) induced linear differentiations (G-bands).The isoschizomers Hpa Ⅱ and Map Ⅰ which recognize 4 base sequences resulted in modified C-bands differing from those produced by conventional C-banding.These findings clearly show that restriction endonucleases are capable of producing G-banding patterns in fish chromosomes and that restriction enzyme digestion can be very useful in the analysis of fish chromatin organizatin.