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"Fertilized eggs of Indian major carp, Cirrhinus mrigala, were subjected to coldshock for a period of 10 minutes at 12, 15 and 18�C. Heatshock at 40�C was also given for 1 minute to fertilized eggs 5 minutes after fertilization. Chromosome analysis indicated that triploid was produced in all the treatments given. The results also indicated that the induction of triploidy was more in heatshock than in coldshock. Among the coldshock treatments the shock given at 15�C produced more triploid as evidenced from high frequency of triploid spreads. The average modal value for diploid mrigal is 50 chromosomes with 40 percent occurrence and that of triploid is 75 chromosomes in 40 percent of the spreads analysed. It is evident that the temperature shock can be used as a simple technique to produce triploid major carps."