The optimation of heat shock was studied to induce triploidy in brown trout,Salmo trutta.The heat shocks were administrated 5 minutes after fertilizationat temperatures ranging from 26 to 28℃ with the duration time ranging from10 to 30 minutes.The karyological examination and survival rate of embryoshad been done to evaluate the efficiency of triploid induction.Moderate tohigh triploidy rates(70% to 94%)were observed in all tests.If the triploidinduction rate and survival rate were concerned together,temperature at 28℃and a duration of 10 or 15 minutes,applied 5 minutes after fertilization gavethe best performances.