Data from the National Ambulatory Medical Care Survey show that the majority of psychotropic drugs and "psychotherapy/therapeutic listening" provided to adults in office-based primary care are given in visits during which no diagnosis of mental disorder is recorded. This finding is not explained either by a general tendency of surveyed physicians to record drug treatment without an appropriate diagnosis or by management of specific nonmental disorders with mental treatments. Patients who receive treatment without diagnosis tend to be older, established patients with established diagnoses who see the physician for a shorter visit and are more likely to have a follow-up appointment. The data do not provide evidence as to whether mental treatment without mental diagnosis results from inadequacies in the current diagnostic system, inadequacies of physician knowledge and skills, or other factors. Further clarification of this issue will require new research models.