The objective of this study is to examine the impact of a clinical reminder generated by an electronic medical record (EMR) system on physician prescribing behavior in community oncology practice setting. A case-control trial assessing the prescribing rates of erythropoietin by physicians is used. The participants and setting involves a total of 11,644 physician-patient encounters in 2 community oncology practices in the United States during a 21-month period. The intervention is a clinical reminder generated in real time during a physician-patient encounter by an EMR identifying cancer patients with low hemoglobin (Hgb) levels (ie, anemic), that is, patients with Hgb less then 12 g/dL. The main outcome measure is to determine the frequency of erythropoietin prescription by physicians to cancer patients with low Hgb levels. Implementation of a clinical reminder generated by way of an EMR significantly improved the likelihood of low-Hgb patients receiving treatment with erythropoietin. Low-Hgb patients in the experimental clinic during the time that the clinical reminder system was in place were almost twice as likely (ie, adjusted odds ratio = 1.92, P = .008) to have been treated with erythropoietin. The data support the effectiveness of clinical reminders as a way to influence physician prescribing behaviors and potentially improve the quality of patient care. However, we feel that there is a need to investigate the use of reminders in other aspects of cancer care that may be undertreated or when new drugs may be available but are underused.