Restriction fragment length polymorphism (RFLP) markers were used to map male fertility restor- ing gene that was transferred from chromosome 6U of Aegilops umbeIIulata Zhuk. to wheat. Segments of ehro-mosome 6U bearing the gene that restore fertility to T. tirnopheevi Zhuk. male sterile'cytoplasm were identified in all four translocation lines by two probes, BCD2t and BCD342. Lines 040-5, 06 l-I and 0614 are T6BL.6BS-6U translocations, while Iine 2114 is a T6AL.6AS-6U translocation, Line 211~ has a much larger 6U chromo-somal segment and lower frequency of transmission of male gametes with the alien segment than the other three lines The restoring gene carried by the 6U segment in 2114 showed high expressivity and complete penetrance. This restoring gene is designated Rf6. A homoeologous chromosome recombination mechanism is discussed for the alien gene transfer