Delivery of best-practice care for posttraumatic stress disorder (PTSD) is a priority for clinicians working with active duty military personnel and veterans. The PTSD Clinicians Exchange, an Internet-based intervention, was designed to assist in disseminating clinically relevant information and resources that support delivery of key practices endorsed in the Veterans Administration (VA)-Department of Defense (DoD) Clinical Practice Guidelines (CPG) for the Management of Posttraumatic Stress. We conducted a randomized controlled trial to examine the effectiveness of the Clinicians Exchange intervention in increasing familiarity and perceived benefits of 26 CPG-related and emerging practices. The intervention consisted of ongoing access to an Internet resource featuring best-in-class resources for practices, self-management of burnout, and biweekly e-mail reminders highlighting selected practices. Mental health clinicians (N = 605) were recruited from three service sectors (VA, DoD, community); 32.7% of participants assigned to the Internet intervention accessed the site to view resources. Individuals who were offered the intervention increased their practice familiarity ratings significantly more than those assigned to a newsletter-only control condition, d = 0.27, p =.005. From baseline to 12-months, mean familiarity ratings of clinicians in the intervention group increased from 3.0 to 3.4 on scale of 1 (not at all) to 5 (extremely); mean ratings for the control group were 3.2 at both assessments. Clinicians generally viewed the CPG practices favorably, rating them as likely to benefit their clients. The results suggest that Internet-based resources may aid more comprehensive efforts to disseminate CPGs, but increasing clinician engagement will be important.