OBJECTIVE Efforts to improve the recognition and treatment of late-life depression in primary care are often based on the assumption that primary care physicians underutilize currently available and effective treatments. This article reviews the validity of this assumption and offers recommendations for future research. METHODS Clinical trials designed to improve the recognition and treatment of late-life depression in primary care are reviewed. Because studies limited to older adults are rare, we also include studies enrolling younger patients. These data are reviewed in the context of recent reviews on the prevalence of depression in primary care settings and the effectiveness of available treatments. RESULTS Although depressive symptoms are common among older adults, there is insufficient literature documenting the proportion of these patients who respond to currently available treatments. Patients with uncomplicated major depressive disorder constitute the minority of primary care patients with depressive symptoms. Nearly all available studies of treatment effectiveness of pharmacotherapy or psychotherapy focus on older adults with uncomplicated major depression. Currently available treatment options may apply to less than 15 percent of depressed primary care patients. CONCLUSIONS More research is needed to help primary care providers manage their depressed patients with comorbid medical conditions, functional disability, or minor or chronic depressions. In addition, more research is needed to identify those patients who would benefit from specialized or interdisciplinary care.