The Meaningful Use criteria promises to make health information exchange (HIE) much more widespread. However, the usage of the information systems made available by existing HIE efforts tends to be very low. This study sought to examine the factors associated with usage of an operational HIE system during ambulatory care visits to safety-net clinics. Overall the HIE system was accessed for 21% of encounters. However, system access took on two distinct forms. In general, usage was more likely for patients with recent emergency department visits and chronic conditions. This study indicates the organizational commitment to engage in HIE does not necessarily mean that the information systems will be always used. In addition, system usage will take on various forms for different reasons. These results reveal considerations for the development, operation and evaluation of HIE efforts.