Anxiety disorders are a major public health concern associated with functional impairment and increased use of the health care system. Two of the more common anxiety disorders are generalized anxiety disorder (GAD) and panic disorder (PD), which if identified, can be treated successfully with medications or psychotherapy. GAD is characterized by at least 6 months of persistent and excessive anxiety and worry that is difficult to control and is accompanied by three of six additional symptoms: restlessness, fatigue, decreased concentration, irritability, muscle tension, and sleep disturbance. PD, on the other hand, is episodic in nature and characterized by recurrent and unexpected panic attacks-periods of intense fear or terror associated with autonomic arousal such as breathlessness, chest pain, or fear of losing control-that become a cause of persistent concern in the patient. Generalized anxiety disorder (GAD) and panic disorder (PD) are two common mental illnesses that present in primary care clinics, often with physical symptoms that can inhibit appropriate diagnosis and treatment. Recognition of these disorders by primary care physicians is much lower than the expected rates-in part due to somatic presentations but also due to the lack of routine screening that is in place for some other mental illnesses. Patients with anxiety disorders are often high utilizers of health care resources, and when their anxiety disorders are not diagnosed and treated, they can frequently undergo more expensive testing to rule out medical causes. Identification of accurate and feasible screening instruments for GAD and PD that have been validated in primary care settings have the potential to improve detection and facilitate treatment of these disorders within the primary care clinic, or to generate appropriate referral. Our report is a systematic review of the literature to evaluate the performance of self-report instruments used to diagnose GAD and PD in primary care settings. Three key questions (KQs) guided this systematic review: KQ 1. In general medical patients with somatic symptoms, what are the performance characteristics (e.g., sensitivity, specificity) of self-report questionnaires for diagnosing generalized anxiety disorder or panic disorder? KQ 2. For questionnaires evaluated in KQ 1, which measures are most feasible to use in primary care settings? Specifically, what is the reading comprehension level, time required to complete, response format, and compatibility with telephone administration? KQ 3. For questionnaires evaluated in KQ 1, do the performance characteristics vary by gender, race, age group, or setting?