Until now, little or no attention has been paid to the monitoring of therapy with nonsteroidal antiinflammatory drugs (NSAIDs). The authors discuss reasons for that situation. They emphasize that lack of monitoring of unwanted side-effects of the widely used NSAIDs is no doubt due to the overuse of these drugs. The expedience and a protocol concerning the efficacy and toxicity monitoring of such drugs are critically discussed. The authors stress that toxicity monitoring should be performed in selected patient groups that to only in those patients at risk.