Prescribing decisions by clinicians are often thought to be simple: a patient's clinical problem leads a prescriber to choose the optimal treatment. However, many factors other than the patient's condition affect prescribing decisions, including the marketing of pharmaceuticals. Clinicians are subjected to direct "detailing" by representatives of the pharmaceutical industry, advertisements in medical journals and requests for specific treatments from patients, who are increasingly exposed to direct-to-consumer (DTC) advertising. These influences, often based on biased or inaccurate information, contribute to a variety of problems in prescribing, including the unnecessary use of expensive, heavily marketed medications.