Spirometry is a useful test of pulmonary function and can be safely performed in a variety of clinical situations. Although the technique for performing the maneuver is straightforward, there are many sources of variability in results. Specific criteria must be met in order for the test to be considered valid. For the best results, proper instruction and coaching is essential, and patient understanding and effort must be maximized. Appropriate interpretation of spirometry requires several steps, including recognition and reporting of technically sound maneuvers, comparison to an appropriate reference population, and finally application of a well-developed interpretation scheme utilized in the context of patient symptoms and findings. Failure at any point along this path from performance to interpretation can yield misleading results that may ultimately poorly impact patient care. A clear understanding by the provider of proper coding and billing for spirometry is necessary to receive appropriate reimbursement from payers.