Our diabetes-specific HPOS intervention incorporates the following key elements: (1) electronic queries of administrative claims to identify patients who are not up-to-date with recommended diabetes services; (2) mail and telephone outreach to alert patients about recommendations for care and facilitate the direct scheduling of primary care provider (PCP) visits, laboratory testing several days before PCP visits, and ophthalmology appointments; and (3) advance PCP notification regarding the intended diabetes focus of appointments arranged through the outreach process. The purpose of this study is to assess whether this intervention improves guideline concordance for LDL cholesterol, hemoglobin A1c, blood pressure, retinal examinations, and aspirin therapy as well as clinical attention to diabetes during primary care visits.