The most common toxicities of nonsteroidal anti-inflammatory drugs (NSAIDs) are gastropathy, renal dysfunction, and liver function abnormalities. We outline an approach to monitoring patients on long-term NSAID therapy, focusing on the early detection of complications. Gastropathy caused by NSAID use is more common in elderly patients or those with a history of dyspepsia, peptic ulcer disease, or alcohol abuse. Fecal occult blood testing and hemograms are less accurate in detecting gastropathy than direct visualization but are convenient and relatively inexpensive. We recommend the periodic use of these tests to detect NSAID-induced acute or chronic blood loss. Renal toxicity is seen in patients with preexisting renal disease or functional volume depletion and in the elderly. Complications include renal insufficiency, hyponatremia, hyperkalemia, and protein-uria. Renal function should be monitored during the first few weeks of NSAID therapy, especially in high-risk patients, with periodic testing thereafter. Hepatic toxicity is less common but warrants occasional determinations of alanine aminotransferase levels. Elderly patients and those with renal insufficiency or alcohol abuse have a higher risk of complications. Nonsteroidal anti-inflammatory drugs should be used cautiously in those patients at high risk for complications. Strategies can be used to limit toxicity. Patients taking these drugs long term should be monitored periodically for signs of blood loss, renal dysfunction, and hepatic dysfunction.