In order to break seed dormancy, different temperatures (20, 30, 40, 50, 60, 70, 80 and 90o C) and durations (10, 20 and 30 minutes) were applied to black locust (Robinia pseudoacacia L.) and honey locust (Gleditsia triacanthos L.) seeds, in the Seed Laboratory of Dicle University - Faculty of Agriculture in 2009. According to the research results, the highest germination rate for black locust seeds was obtained in the case of 90o C for 30 minutes pre-treatment (94.5%), whilst the lowest value was obtained for the 40o C for 10 minutes pre-treatment (7.5.0%). For honey locust the highest value was obtained at 50o C for 30 minutes (25.5%) and the lowest value was obtained in the case of control sample (6.8%).