Institutions of higher education often tout that they are developing students to become lifelong learners. Evaluative efforts in this area have been presumably hindered by the lack of a uniform conceptualization of lifelong learning. Lifelong learning has been defined from institutional, economic, socio-cultural, and pedagogical perspectives, among others. This study presents the existing operational definitions and theories of lifelong learning in the context of higher education and synthesizes them to propose a unified model of college students' orientation toward lifelong learning. The model theorizes that orientation toward lifelong learning is a latent construct which manifests as students' likelihood to engage in four types of learning activities: formal work-related activities, informal work-related activities, formal personal interest activities, and informal personal interest activities. The Postsecondary Orientation toward Lifelong Learning scale (POLL) was developed and the validity of the resulting score interpretations was examined. The instrument was used to compare potential differences in orientation toward lifelong learning between freshmen and seniors. Exploratory factor analyses of the responses of 138 undergraduate college students in the pilot study data provided tentative support for the factor structure within each type of learning activity. Guttman's <λ>λ2 estimates of the learning activity subscales ranged from .78 to .85. Follow-up confirmatory factor analysis using structural equation modeling did not corroborate support for the hypothesized four-factor model using the main student sample data of 405 undergraduate students. Several alternative reflective factor structures were explored. A two-factor model representing factors for Instructing/Presenting and Reading learning activities produced marginal model-data fit and warrants further investigation. The summed POLL total scores had a relatively strong positive correlation with global interest in learning (.58), moderate positive correlations with civic engagement and participation (.38) and life satisfaction (.29), and a small positive correlation with social desirability (.15). The results of the main study do not provide support for the malleability of postsecondary students' orientation toward lifelong learning, as measured by the summed POLL scores. The difference between freshmen and seniors' average total POLL scores was not statistically significant and was negligible in size.