A patient's unique, personal name is fundamental in medical relationships. Sometimes, patients may use false names, which obscure family, ethnic, sexual, or billing identities. The means and motivations involved--fraud, concealment, gaining financial or personal advantage, gratifying a psychic need, or changing group assignment--produce a variety of distinct clinical manifestations of false name use. These may be classified as alias, pseudonym, manipulator, fraud, psychotic, amnestic, medical factitioner, and renamed. The identification of falsely named patients enables clinicians to improve care for these types of patients. Individual cases are briefly described and a discussion of naming in society and medicine follows. This preliminary discussion may serve to fuel further refinement.