Physician forgetfulness, patient refusal, and practice logistical difficulties are among the major reasons that physicians perform cancer prevention activities less frequently than recommended by established guidelines. To improve delivery of prevention services, office system interventions of several types have been developed and tested. These include approaches aimed at patients during the medical encounter (in-reach) and outside the medical setting (outreach). In-reach interventions include medical record checklists and flow sheets, stickers and alerts, audit with feedback, nurse-initiated reminders, and computer-generated reminders, including ones generated by mainframe and microcomputer systems. In-reach interventions are directed at patients alone, at physicians alone, at patients and physicians simultaneously, or at office staff. Outreach reminder interventions include reminder postcards, letters, telephone calls, and questionnaires. Outreach reminders are directed at patients alone. The authors review the literature supporting the efficacy of such office systems. The analysis suggests that office systems are effective strategies in promoting cancer prevention activities.