Appointment attendance for follow-up care and laboratory monitoring are central components of HIV treatment. In general, appointment reminders are an effective method of reducing outpatient no-shows; however, no single strategy has proven superior. This study tested the effectiveness of adding an automated telephone reminder for laboratory monitoring to the standard set of three appointment reminders to reduce subsequent HIV primary care no-shows. We conducted a quasi-experimental design study in three geographically and administratively affiliated Veterans Administration HIV clinics with one clinic serving as the intervention facility and two others as control facilities. The intervention lasted 6 months. The data show that patients who were not homeless, who were not diagnosed with depression, and who had five or more appointments scheduled in 6 months had significantly fewer no-shows after intervention. The intervention was not effective in reducing no-shows among homeless patients, racial/ethnic minorities, and patients with mental health disorders.