The World Health Organization has identified the integration of mental health into primary care as the most salient means of addressing the burden of mental health conditions, noting its "urgent importance." In the United States, half of the care for common mental health disorders is delivered in general medical settings, emphasizing the vital role that primary care providers play in the diagnosis and treatment of these disorders. Common mental health conditions, such as depression and anxiety, are found in up to 10 percent of primary care patients, and these conditions often coexist with chronic medical conditions. Accordingly, considerable interest has been expressed in improving the recognition and management of mental health conditions, especially depression, within primary care. Specifically, interest is emerging about whether treatment of common mental health conditions in primary care can improve both mental health and chronic medical outcomes. The arena of mental health and primary care is moving from consideration of single conditions and their outcomes to more real-world, complex-care paradigms. However, to date, no synthesis of the evidence on practice-based interventions accounts for the primary care patient with "multiple chronic conditions" and examines both mental health and chronic medical outcomes simultaneously. Despite the prevalence and importance of other mental health conditions in the primary care setting, especially anxiety, substance use, and psychotic disorders, our preliminary review of the literature revealed that only depression has the evidence base necessary to meet eligibility criteria for a comparative effectiveness review. The purpose of this report, therefore, is to summarize the available evidence on the effectiveness of practice-based interventions aimed at adult primary care patients with concomitant depression and chronic medical diagnoses. We believe this will add to the literature by (1) synthesizing data on mental health outcomes among people with defined chronic medical conditions, and (2) synthesizing data on chronic medical outcomes among these same people. As we conceptualized the approach to this report through the topic nomination and refinement process, preliminary evidence reviews revealed insufficient data on mental health conditions other than depression that met all eligibility criteria. We specifically searched for evidence in patients with anxiety, but no studies met final eligibility criteria. The exclusion of mental health conditions other than depression does not reflect a belief that they are less important, but that the literature is not mature enough to answer the questions set forth. This review therefore summarizes the body of evidence that examines the effectiveness of practice-based interventions aimed at improving depression or both depression and chronic medical conditions in adult primary care patients with depression and chronic medical condition(s) at baseline. The inclusion criteria require a level of depression that exceeds generally accepted cut points for major depression on common instruments, but were not necessarily confirmed by gold standard evaluations. We use the term depression throughout the report to reflect this definition. In an effort to address the inherent heterogeneity of complex interventions, this report also compares the specific characteristics of the interventions and the practice settings in which they are delivered.