Genotype and environment (G x E) interactions are of major concern to plant breeders in breeding cultivars. The objective of this study was to determine the stability of grain yield in 12 wheat genotypes. Eleven lines selected from Tir wheat population (Triticum aestivum) were used in the study. The experiment was conducted in Van, Ercis, and Adilcevaz located in the eastern part of Turkey in 1997-98 and 1998-99. Two stability parameters were obtained as linear regression coefficient (b) of an entry mean on the average of all entries and deviation from regression (s(2)d), then stability was tested with the hypotheses b = 1.0 and s(2)d = 0. The results indicated that there were significant differences and interactions among genotypes, locations and years. The regression coefficient (b) values of the 11 genotypes used in this study ranged from 0.46 to 1.73; deviation from regression ranged from 69.9 to 2896.7. According to estimates of the two stability parameters, none of the genotypes were stable for grain yield. However, based on the linear regression coefficient and average grain yield, line 2 (Adilcevaz-40/1) and 11 (Van-Edremit/1) appeared to be promising because their yields were above the average in all of the environmental conditions of this study.