Powdery mildew caused by Blumeria graminis f.sp. tritici is significantly affecting wheat production worldwide. In the search for new sources of resistance we investigated the powdery mildew resistance in the synthetic hexaploid wheat line "Synthetic 43" with its D genome from Aegilops tauschii. This line was developed at CIMMYT and resists a number of common bread wheat diseases. The line was crossed with the powdery mildew susceptible hexaploid wheat cultivar WH542 and a mapping population consisting of 148 RILs was developed. Inheritance studies in the RIL population revealed monogenic inheritance of powdery mildew resistance both at the seedling stage and adult plant stage. This resistance gene was mapped at a distance of 4.8 cM from SSR marker Xwmc150 on chromosome 7D and has been temporarily designated as PmT.