Nonsteroidal anti-inflammatory agents (NSAIDs) are the most commonly encountered over-thecounter (OTC) and prescription medications in physical therapy practice. Worldwide, over 73 000 000 prescriptions for nonsteroidal agents are written yearly. NSAIDs produce a wide range of beneficial effects to the physical therapy patient, enhancing the outcome of treatment. Helpful effects of NSAIDs include analgesia, antipyretic, anti-inflammatory, and antithrombotic properties. However, NSAIDs are also associated with frequent and significant side effects that are deleterious to treatment outcome, including delay in soft tissue and bone healing, renal and liver toxicity, hemorrhagic events, gastric irritation and ulceration, and central nervous system effects. Understanding of the pharmacological properties of these drugs, exemplified by aspirin, and the individual pharmacokinetics of specific preparations will help the therapist to screen patients for potential side effects, develop more effective plans of care, and, where allowed, effectively and safely prescribe NSAIDs. J Orthop Sports Phys Ther 2005;35:356-367.