Frequently interacting with other people or working in an information-rich environment can foster the "accidental discovery of information" (ADI) (Erdelez, 2000; McCay-Peet & Toms, 2010). With the increasing adoption of social web technologies, online user-participation communities and user-generated content have provided users the potential for ADI. However, ADI on the Social Web has been under-examined in the literature of library and information science. This gap needs to be addressed in order to get a more complete picture of human information behavior. The objectives of this dissertation were to develop the propositions that describe and explain ADI behaviors among individual users of web-based social tools. Two research questions were addressed: (1) What are the characteristics of ADI on the Social Web? (2) What are the users' perceptions about ADI on the Social Web? This dissertation used a sequential mixed-method research design involving three data collection methods: a survey, and follow-up logs, and interviews. The sample includes 45 participants in an academic environment. Among the survey participants, a purposeful sample of 13 individuals completed follow-up incident logs and in-depth interviews. Qualitative analysis with Stata 12/MP (StataCorp, 2011) and qualitative analysis with ATLAS.ti v.6 (http://www.atlasti.com/) were performed on the data. The results presented include descriptive statistics and thematic findings. The important findings include: (1) ADI on the Social Web has many unique characteristics that can be identified within the six elements of "user," "motivation," "context," "information behavior," "information," and "information need"; (2) participating users considered the Social Web as a useful environment for ADI, and they even used some self-developed strategies to facilitate ADI; (3) prior experience and anticipation of ADI can be the motivations to use particular social tools; (4) social tools can serve as information grounds where users gather together and form relations, precipitating conditions which foster ADI; (5) users considered ADI on the Social Web as supplementary to their overall information acquisition; the unexpected information that they found was most beneficial for addressing long-term information needs. The findings of this study expand on existing information behavior theories and offer practical insights for the design of information services and library instruction. [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.]