guideline in collaboration. A joint ACP-ASIM/ACCP expert panel examined the evidence and developed recommendations. The guideline and accompanying background article are primarily based on a systematic review compiled in an Agency for Health Care Research and Quality evidence report prepared by the Evidence-Based Practice Center at Duke University.1 Our target audience is primary-care physicians and specialists who care for COPD patients. Although the majority of acute exacerbations of COPD (AE-COPD) take place and are treated on an outpatient basis, the research studies all focus on emergency department (ED) or inpatient settings. As a result, this guideline applies to exacerbations treated in those settings. The guideline presents the available evidence on the following: 1. Risk stratification for relapse, and 6-month mortality. 2. Diagnostic testing for AE-COPD. 3. Current treatment options for AE-COPD. Currently in the United States, 16 million adults have COPD, accounting annually for 110,000 deaths, . 16 million office visits, 500,000 hospitalizations, and $18 billion in direct health-care costs. COPD is characterized by chronic airflow obstruction and episodic increases in dyspnea, cough, and sputum production that are commonly called “exacerbations.” After an acute exacerbation, most patients experience a decrease in quality of life, transitory or permanent, and nearly half of patients discharged are readmitted to the hospital more than once in the following 6 months. Thus, one of the main treatment goals for COPD patients is to reduce the number and severity of exacerbations they experience each year. There is no widely accepted definition of acute exacerbation of COPD, but most published definitions encompass some combination of three clinical findings: worsening dyspnea, increase in sputum purulence, and increase in sputum volume. A severity scale for acute exacerbations, developed by Anthonisen and colleagues,2 is based on these finding as well as others. Type 1 exacerbations (severe) have all three of the above symptoms; type 2 exacerbations (moderate) present with two; and type 3 exacerbations (mild) have one of these, plus at least one of the following: an upper-respiratory-tract infection in the past 5 days, fever without other apparent cause, increased wheezing, increased cough, or increase in respiratory rate or heart rate by 20% above baseline. We will use this scale when referring to severity in this guideline. Acute exacerbations can be triggered *From the American College of Physicians-American Society of Internal Medicine and the American College of Chest Physicians. This paper also appears in the Annals of Internal Medicine 2001; 134:595–599. †A complete list of participants is given in the Appendix. Disclaimer: The authors of this article are responsible for its contents, including any clinical or treatment recommendations. No statement in this article should be construed as an official position of the Agency for Healthcare Research and Quality or the US Department of Health and Human Services. Manuscript received August 1, 2000; accepted August 2, 2000. Correspondence to: Vincenza Snow, MD, American College of Physicians-American Society of Internal Medicine, 190 N. Independence Mall West, Philadelphia, PA 19106; e-mail: Vincenza@ Mail.acponline.org special report