Nonsteroidal anti-inflammatory drugs (NSAIDs) annually account for 70 million prescriptions and 30 billion over-the-counter (OTC) medications sold in the United States alone. Despite our familiarity with these drugs, NSAIDs are full of paradoxes that pose significant challenges for the medical community. Although NSAIDs are among the oldest of drugs, new formulations continue to come to market. Some formulas are safe enough to be sold OTC for use in infants with fever, while others are available only as a prescription medication and are a leading cause of iatrogenic reactions, hospitalizations, and death. Physicians face the choice of prescribing lower cost, older NSAIDs versus the more expensive but potentially safer ones. The use of NSAIDs is clearly increasing. Factors contributing to this increase are the availability of OTC preparations and the aging of the population with a concomitant increase in osteoarthritis. One indication of the popularity of NSAIDs is that following the introduction of 2 new cyclooxygenase-2 (COX-2) selective inhibitors in 1999, these drugs immediately became the most frequently prescribed new drugs in the United States. This article will familiarize the practitioner with the various types of NSAIDs, including the newer COX-2 formulations, their mechanism of action, and potential adverse reactions and efficacy. Although most practitioners are aware of the indications for NSAIDs, research is continuing to explore nontraditional applications. A new framework is being created that will allow new additions to the NSAID class of medications.