More than 30 million Americans have chronic obstructive pulmonary disease (COPD) and asthma, with internists, pediatricians, and family physicians providing most of their medical care. Recent management guidelines for asthma and COPD recommend regular use of spirometry for the diagnosis and management of these disorders. Because of the development of easy-to-use office-based spirometers, an increasing number of physicians have ready access to spirometry. Beyond simple spirometry, various tests are available from many pulmonary function laboratories for more detailed evaluation of patients with respiratory disorders. For these reasons, all physicians who care for patients with pulmonary disease must understand basic pulmonary function testing and have a fundamental understanding of more sophisticated tests. A series of performance standards has been developed for improved accuracy and precision of pulmonary function tests. Physicians responsible for administering and interpreting pulmonary function tests, even simple spirometry, must be aware of relevant guidelines. This concise review addresses current indications for pulmonary function testing, provides an overview of the studies commonly available in modern pulmonary function laboratories, and includes comments on basic interpretation and testing standards.