OBJECTIVES: To evaluate whether community pharmacists have the ability to influence prescribing decisions and to determine the extent to which they do so. DATA SOURCES: International Pharmaceutical Abstracts was searched for articles published between January 1970 and September 2002 and MEDLINE was searched for articles published between January 1966 and September 2002 that contain the terms pharmaceutical care or pharmacist and intervention. STUDY SELECTION: Selected studies documented pharmacist interventions that resulted in a change in prescribing that required influencing the prescriber, included a complete description of methods and results, and were conducted in community pharmacies in the United States. DATA EXTRACTION: Selected studies were examined to determine whether, in what ways, and to what extent community pharmacists influenced prescribing. DATA SYNTHESIS: Community pharmacists in traditional practices regularly, but infrequently, recommend to prescribers that they initiate, discontinue, or change drug therapy. Prescribers usually accept and implement pharmacists' suggestions. Pharmacists are more likely to intervene to correct drug therapy problems when they have been trained to provide pharmaceutical care and have modified their practices to accommodate a more patient-centered style of practice. In the larger reviewed studies, pharmacists intervened to change therapy for the majority of their patients. CONCLUSION: Community pharmacists routinely intervene to influence prescribing. They do so, for the most part, to correct clinical problems or to provide their patients with more affordable therapy. In the majority of interventions, physicians accept and implement pharmacists' suggestions.