This dissertation evaluated the provision of two different one-to-one educational interventions, randomly assigned, to two separate groups of medical practitioners at a health maintenance organization (HMO), Cigna Healthplan of Tucson, Arizona. A control group received no intervention. Each group consisted of seven physicians and one nurse practitioner. The intervention was aimed at improving the prescribing of the anti-ulcer drugs, cimetidine, ranitidine, and sucralfate. The theoretical basis for the study involved the cognitive principle of vividness, which implies that more vivid information has greater effect on decisions. For this research, the vivid intervention included case scenarios, while the non-vivid intervention included statistical information of the results of a drug use review. Prescribing data, consisting of percentages and cost of inappropriate prescriptions, were collected for one month prior to and for two months after the intervention. Analysis of covariance was employed with the pre-intervention measures of prescribing as the covariate in each test and post-intervention measures as the dependent variables. No differences were found between the two interventions, but the control group was significantly different from the intervention groups. For the first post-intervention month, it was found that the interventions resulted in significantly lower percentages of prescriptions written inappropriately for indication, dose, or duration (P = 0.001). These percentages decreased by 36% for the intervention groups, while increasing by 14% for the control group. Costs of inappropriate prescribing per study prescription and per patient encounter were also significantly lower for the intervention groups than for the control group (P = 0.001 and P = 0.019, respectively). In the second post-intervention month, inappropriate prescribing increased slightly in the intervention groups and were no longer significantly different from the control group. The research demonstrated the effectiveness of a one-to-one educational intervention in improving drug prescribing at an HMO. The lack of differences between the two interventions may have been due to the overall effectiveness of the one-to-one educational discussion, the interpretation of the statistical information as prescribing feedback by the practitioners, or the inadequate presentation of vividness in the case scenarios.