Purpose: This study examined how repeated presentations of lexically difficult words within a background noise affect a listener's ability to understand both trained (lexically difficult) and untrained (lexically easy) words in isolation and within sentences. Method: In the 1st experiment, 9 young listeners with normal hearing completed a short-term auditory training protocol (5 hr) while 8 other young listeners with normal hearing completed a similar protocol lasting about 15 hr in the 2nd experiment. All training made use of multiple talkers and was in a closed-set condition. Feedback was provided on a trial-to-trial basis and consisted of either orthographic or orthographic and auditory feedback. Performance on both the trained and untrained words in isolation and within sentences was measured pre- and posttraining. Results: Listeners' performance improved significantly for the trained words in an open and closed-set condition, as well as the untrained words in the closed-set condition. Although there was no mean improvement in the number of keywords identified within sentences posttraining, 50% of the listeners who completed the long-term training showed improvement beyond the 95% critical difference. Conclusions: With enough training on isolated words, individual listeners can generalize knowledge gained through isolated word training to the recognition of lexically similar words in running speech.