BACKGROUND Strategies to control the quality and cost of medication use are largely dependent on the ability to alter selection of medications. Previous models of prescribing behavior have focused on physicians. In the hospital setting, clinical pharmacists and formulary committee members are also key players in drug therapy decision-making. Differences between physicians, formulary committee members, and clinical pharmacists have not been compared. Knowledge of these differences could have importance in predicting the effectiveness of strategies designed to influence drug use in this setting. OBJECTIVE To describe and compare the opinions of physicians, clinical pharmacists, and formulary committee members with respect to key factors that influence medication prescribing in community hospitals. METHODS Physicians, clinical pharmacists, and formulary committee members were solicited to participate. A trained interviewer administered a standardized questionnaire designed to elicit opinions of participants regarding the importance of factors thought to influence drug prescribing. Responses were described using descriptive statistics, and differences between the groups were determined by post hoc analysis. RESULTS A total of 150 individuals participated in the study. Safety, effectiveness, formulary status, and restrictions on prescribing were considered highly influential by all participants. Physicians rated the availability of drug samples and personal experience higher (more influential on prescribing) than clinical pharmacists and formulary committee members. Clinical pharmacists and formulary committee members rated the influence of recommendations by clinical pharmacists, prescribing guidelines, and cost or cost comparisons higher than physicians. Factors that were drug-related or that involved policy-related programs tended to be more influential than indirect factors. CONCLUSIONS Those who seek to implement programs to alter medication use should recognize and employ factors that are most influential in the decision-making process. Further, it may be important to consider differences that exist between key participants in the medication use process.