The medical model is associated with a variety of professional interventions. These include genetic counseling, to advise parents on possible risks to their natural children when familial patterns of psychopathology have been identified. It is associated with neurology and neurosurgery and with the technical advances in medical imaging that give unprecedented nonintrusive access to anatomical structures and physiological processes. And it is associated above all in the public mind with prescribing and dispensing medicationpharmaceutical products designed to treat practically any recognized mental disorder. In appraising the biological model fairly and accurately, psychologists face the challenge of deciding where in the spectrum of possible viewpoints-from an exclusive biological determinism to a single-minded emphasis on psychological and environmental causation-lies the most defensible position. This is made the more difficult because of some common logical errors that can be too uncritically accepted by the unwary.