Tan spot, a foliar disease of durum and common wheat, causes 5-15% yield losses and adversely affects the quality of grain. On susceptible hosts, P. tritici-repentis induces two phenotypically distinct symptoms, tan necrosis and chlorosis. The objectives of this study were to determine the inheritance of resistance to tan necrosis caused by P. tritici-repentis, race 1, in tetraploid wheat line T. turgidum # 283, and hexaploid wheat genotypes, Synthetic Hexaploid Elite # 1, Synthetic Septoria # 57, Intros # 7, 2000 Spelt # 20, and CIMMYT L # 18. Additionally the allelic relationship between the resistance gene(s) possessed by these genetically diverse resistant sources was also determined. The F1, and F2 plants and F2:3 families of resistant/susceptible and resistant/resistant crosses were studied under controlled environmental conditions. Plants were inoculated at the 2-leaf stage and disease reaction was assessed eight days after inoculation based on 1-5 lesion type scale. Tests of the F1 and F2 generations and of F2:3 families indicated that one recessive gene controlled resistance to the necrosis component of tan spot caused by race 1 in each cross studied in both tetraploid and hexaploid wheat. Lack of segregation in crosses between the resistant cultivars indicated that the resistance gene was the same in all the cultivars.