New cotton (Gossypium hirsutum L.) seeds that can produce fiber with enhanced strength would increase efficiency of the rotor form of open end yarn manufacture. We report results of 3-yr of breeding transgenic `Deltapine 50' (DP 50) germplasm expressing enhanced fiber strength. The objective was to identify germplasm that could consistently express and transmit enhanced fiber strength to their progeny. Deltapine 50 cotton was transformed via particle bombardment of meristems by Monsanto. The intent of transformation was to insert a b-glucuronidase (GUS) marker gene and a proprietary gene driven by a fiber specific promoter. The R4-R6 generations descendent from three GUS-positive, enhanced strength, R3 greenhouse plants were evaluated in the field from 1996-1998 near Florence, SC. Unusual frequencies of GUS-positive progeny were found upon self-pollination of GUS-positive plants, possibly reflecting altered fitness of transgenic gametes. Fiber strength of most GUS-positive plants was 30-70% greater than the non-transformed DP 50 control plants. After examining numerous parent-offspring relationships, we did not observe any consistent transmission of enhanced fiber strength. Results of this study, however, may have application to other transgenic cotton breeding efforts.