ABSTRACT: Background and Objectives:There is growing evidence of the benefits of computers for older adults. Yet, adoption rates are lower compared with younger adults. Extant theoretical models of technology acceptance are limited in their application to older adults-studies on which these models are based included a limited sample of older adults or none at all; none assessed use of a technology specifically designed for older adults; and most only measured intention to use a technology or short-term use, rather than longer-term use (i.e., adoption). We assessed adoption of a computer system specifically designed for older users, for a diverse sample, over an extended period of time. Research Design and Methods:We analyzed archival data from 150 ethnically diverse older adults (65-98 years of age) who participated in the Personal Reminder Information and Social Management (PRISM) randomized controlled trial (Czaja SJ, Boot WR, Charness N, Rogers WA, Sharit J, Fisk AD,…Nair SN. The personalized reminder information and social management system (PRISM) trial: Rationale, methods and baseline characteristics. Contemp Clin Trials. 2015;40:35-46; Czaja SJ, Boot WR, Charness N, Rogers WA, Sharit J. Improving social support for older adults through technology: Findings from the PRISM randomized controlled trial. Gerontologist. 2017;58:467-477). We examined the extent to which attitudes, personal characteristics (e.g., age, gender, and personality), and cognitive abilities predicted mid-term and long-term adoption of a computer system designed for older adults. Results:There were individual differences in PRISM use over time. Regression analyses indicated that individual differences in earlier use of the system, executive functioning, and computer efficacy predicted long-term use. Discussion and Implications:These data provide insights for broader-based models of technology acceptance to guide design, instruction, and deployment of products for older adults. Specifically, the provision of opportunities to foster efficacy and gain positive experience with computer technologies may play a critical role in the likelihood that older adults adopt such technologies. Trial Registration:NCT01497613.