The association of some nonsteroidal anti-inflammatory drugs (NSAIDs) with adverse effects on renal function has led to the need to systematically determine the risk of clinically relevant renal effects in patients treated with these drugs. Tenoxicam, an NSAID with established efficacy in the treatment of rheumatic diseases, has been studied in a variety of patient populations to evaluate its effects on renal function. Investigational studies, up to 5 years' duration, evaluated glomerular filtration renal blood flow and tubular function. There was no evidence of clinically relevant renal toxicity in patients with normal renal function, in elderly patients with age-related renal function, or in patients with mild to moderate renal impairment. There was, however, one patient with pre-existing renal pathology, who experienced raised plasma creatinine after 5 years of treatment. These findings are supported by an analysis of urinary system adverse effects in clinical trials that included over 67,000 patients, 25% of whom were elderly. The prevalence of these events, 0.07%, was similar in patients in both age groups. The most common events were dysuria and renal pain. Thus, patients treated long term with tenoxicam are at low risk for nephrotoxic effects. It is not recommended, however, that patients with severe pre-existing renal insufficiency receive tenoxicam.