A considerable body of knowledge noe exists in the area of depressive disorders in primary care. Primary care clinicians appear to identify less than half of patients with major depressive disorder and adequately treat only a portion of those they identify. However, recent research suggests that identification and treatment of depressive disorders in primary care is a far more complex process than previously assumed. The presence of significant differences in patient expectations, the process of care, and the clinical epidemiology of depression between psychiatric and primary care settings makes it difficult to interpret existing studies of primary care clinician performance. This paper describes an alternative conceptual model for the identification and management of depression in primary care which incorporates the concept of "competing demands" derived from the preventive services literature. The central premise of this model is that primary care encounters present competing demands for the attention of the clinician and that there is not enough time to address each demand. The identification and treatment of depression represents an active choice from multiple clinician and patient priorities such as treatment of acute illness, provision of preventive services, and response to patient requests. Choice is influenced by three sets of interrelated "domains," representing the clinician, the patient, and the practice ecosystem. Each domain is indirectly influenced by the general policy environment. Detection and treatment of depression in this model occurs over time as clinicians work through these competing demands. Although the competing demands model contains many unproven elements, it is likely to have a great deal of "face validity" for practicing primary care clinicians, and its validity can be empirically tested. Using the model as a framework to guide inquiry into the identification and management of depression and other mood disorders in primary care may lead to the discovery of more creative and effective solutions to the problem of underdiagnosis and undertreatment.