Non-steroidal anti-inflammatory drugs (NSAIDs) are the most frequently used drugs, either on prescription or over-thecounter (OTC). Their daily dosage is based on randomised controlled trials and an empirical clinical assessment of their efficacy and toxicity that allows dose adjustment. The individual response can however be altered by environmental and genetic pharmacokinetic and pharmacodynamic factors. This review summarizes the available pharmacogenetic data that explains part of the variability in response and occurrence of adverse drug reactions to NSAIDs treatment, with a thorough focus on CYP2C9, uridine diphosphate glucuronosyltransferases (UGTs) and cyclooxygenases (COX1 and COX2). Other polymorphisms that are currently being studied and could also explain the interindividual variability in the efficacy and safety of NSAIDs will also be considered.