Using fiscal and administrative data routinely collected by the Tennessee Medicaid program, we conducted epidemiologic analyses of physicians' prescribing of selected antibiotics in office practice. This research has defined several subgroups of physicians who regularly malprescribed chloramphenicol or tetracyclines (to children less than 8 years old). After special educational mailings to all physicians, prescribing of these antimicrobial drugs diminished. Similar analyses could enable the profession to design specific remedial educational interventions, target them at physicians needing contemporary information, and assess their impact by monitoring subsequent prescribing. Such a program might diminish inappropriate drug use, reduce adverse drug reactions, help contain medical care costs, and produce better educated physicians.