Academic librarians are encouraged to provide library services, resources, and instruction to all patrons, including the adult learner. Statistics reported that worldwide, adults are a growing student population in colleges and universities; however, the adult learner as an academic library patron is often neglected. Academic libraries can establish value to its stakeholders and support the information needs of adult learners through an active commitment to the process of web-based information literacy instruction that includes outcomes assessments. The purpose of this study was to examine academic librarians' practices and perceptions on web-based instruction for academic library patrons as adult learners. Three research questions guide this mixed-method study. The first research question focused on forms of web-based instruction. The second research question examined the Association of Colleges and Research Libraries (ACRL) "Information Literacy Competency Standards for Higher Education." The third question explored the use of outcomes assessments in web-based instruction. Quantitative data were collected through use of a survey distributed to the ALA's Information Literacy Instruction Electronic Discussion List (ILI-L). The qualitative method gathered academic librarians' practices and perceptions through semi-structured interviews. Six themes emerged from the semi-structured interviews: (1) web-based instruction practices, (2) rationale for use, (3) instructional methods and strategies, (4) information literacy competency areas, (5) information literacy competency standards, and (6) formative and summative assessments. The findings, survey results, and emerging themes suggested implications for practices and further research on outcomes assessments in web-based instruction. There is also a significant need for more web-based instruction designed specifically for the adult learner. These suggestions concern all academic librarians involved in the distribution and development of web-based instruction. Additionally, the interpretations and recommendations for future research were presented. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]