Non-attendance reduces clinic and provider productivity and efficiency, compromises access and increases cost of health care. This systematic review of the English language literature (November 1999-November 2009) compares telephone, mail, text/short message service, electronic mail and open-access scheduling to determine which is best at reducing outpatient non-attendance and providing net financial benefit. Telephone, mail and text/short message service interventions all improved attendance modestly but at varying costs. Text messaging was the most cost-effective of the 3, but its applicability may be limited. Few data are available regarding electronic mail reminders, whereas open-access scheduling is an area of active research.