Health information exchange (HIE) is the process of electronically sharing patient-level information among different organizations with the objectives of quality and cost improvements. The adoption of HIE in the United States is not widespread, but numerous efforts at facilitating HIE exist and the incentives for electronic health record system usage in the American Recovery & Reinvestment Act increases the number of providers who will be engaged in the process. Using diffusion of innovation theory as an overarching framework, this dissertation examines the factors associated with adoption, implementation and effectiveness of HIE in three separate studies. The first study demonstrates that factors beyond the technological are associated with hospitals’ adoption and implementation of HIE. Specifically, competition is negatively associated with implementation. The second study, using data from an operational HIE, examines the factors associated with individual usage of an HIE system. For emergency department encounters, usage of HIE systems was negatively affected by how busy the facility was that day and if the patient had been to that department previously. Results suggest providers utilize the system to help find more appropriate sources of care for frequently seen patients. The third study, examines the question of whether or not usage of an HIE was associated with improvements in patient utilization patterns. Although system usage was associated with older patients, those with more comorbidities and patients with frequent prior utilization, usage was not negatively associated with emergency department usage, inpatient hospitalizations or hospitalizations due to ambulatory care sensitive conditions. The results of these three studies provide guidance on improving policy surrounding and operation of HIE efforts. First, numerous barriers exist at the organizational and individual level to widespread effective HIE. Additionally, even once implemented, usage of HIE systems may minimal. Low levels of usage, or barriers to individual usage, may make it hard for evaluators and organizations to find beneficial effects for their patients. In order to see anticipated benefits, national policy must encourage broad and easy information sharing and organizations must fit system usage into existing work processes so that system usage can meet the needs of users.