Plasmons (= cytoplasms) of eight Triticum species (ten accessions) and 24 Aegilops species (36 accessions) have been introduced by repeated backcrosses to 12 genotypes of hexaploid, common wheat. At transfer problems such as crossing barrier, preferential transmission of a gametocidal or parthenogenesis-inducing chromosome, and mistagging of the material occurred, all of which hindered the plasmon transfer program. Of the 552 genotype-plasmon combinations produced, 532 (96.4%) had reached the B₁₀ or a later backcross generation, 15 (2.7%) the B₇~B₉ generation, and the remaining 5 (0.9%) the B₄~B₆ generation by summer, 1996. Pollen and selfed seed fertilities were observed in plants of all the field-grown lines in the 1992 - 1993 winter crop season, and backcrossed and selfed seed fertilities of plants grown in a greenhouse under a long day condition (17-h light) were assessed in the five latest backcross generations. Selfed seed fertility was found to be a better parameter of male fertility than was pollen fertility. Female fertility, as estimated from the backcrossed seed fertility, was about three times more tolerant to genetic stress caused by the alien plasmon transfer than was male fertility evaluated from both the pollen and selfed seed fertilities. The plasmons studied could be classified into 14 fertility spectrum groups. Most, excluding 15 plasmons belonging to the B, D, D², S, and S^b plasmon types, were considered the male sterile plasmon to common wheat.