Pm6 transferred from Triticum timopheevii L. to common wheat, is an effective resistance gene to powdery mildew disease caused by Erysiphe graminis f. sp. tritici. The RAPD technique, employing a total of 700 decamer primers, was used to identify polymorphic markers between resistant (IGVI463) and susceptible (Prins) near-isogenic lines. Primer OPV20 produced a 2,000 base pair (bp) reproducible fragment only in the resistant near-isogenic line. The 2,000-bp DNA fragment was present in all other introgression lines containing Pm6. Using the F2 mapping population from a cross of IGVI-463 (PI170914/7*Prins) x Prins, Pm6 was shown to be closely linked to the marker OPV20-2000 at a genetic distance of 3.0 +/- 2.2 cM. The marker was successfully used in detecting the presence of Pm6 in different genetic backgrounds.