A wearable, fully digital, personal processing unit developed for the study of hearing aid fitting and digital signal-processing techniques was utilized in a preliminary study of hearing aid fitting validation. In a modified single-subject, multiple-baseline control design, 12 hearing-impaired listeners indicated their preferences for monaurally aided frequency response alternatives during an initial laboratory session, a real-world session, and a final laboratory session. Listeners' preferences, based on listening to connected speech, were stored in each environment by the personal processing unit. Within blocks of 3 each, subjects were time-lagged with respect to the number of trials to criterion. Subjects participated in 1 of 4 listening conditions, classified according to laboratory stimulus materials: speech recorded in an audiometric sound room in quiet or noise, and speech recorded in a reverberant room in quiet or noise. When compared with preferences obtained in the initial laboratory session, preferences obtained during the final laboratory session agreed better with those obtained in the real world. Overall, however, preferences under laboratory conditions were only fair predictors of preferences under everyday conditions. Results reveal the potential of harnessing the programming and storage capabilities of digital signal-processing technology in implementing new hearing aid fitting strategies.