I examine the importance of physicians in the process by which patients receive either trade-name or generic drugs. Using a dataset on physicians, their patients, and the multisource drugs prescribed, I find that almost all physicians prescribe both types of drugs to their patients, but some physicians are more likely to prescribe generic drugs while other physicians are more likely to prescribe trade-name drugs. Very little of the prescription decision can be explained by observable characteristics of individual patients, but all of the evidence indicates that physicians are indeed an important agent in determining whether patients receive either trade-name or generic drugs.