A randomized trial of the effect of three non-steroid anti-inflammatory agents in ameliorating cancer-induced fever. Paraneoplastic fever is well known, and is not an uncommon problem in daily practice. In an effort to ameliorate tumour-induced fever we randomized 48 patients to receive three different non-steroid anti-inflammatory drugs: Naproxen (500 mg d-1), Indomethacin (75 mg d-1) or Diclophenac sodium (75 mg d-1). All patients had solid tumours, and microbial infection had been excluded. All three drugs were equally effective in bringing the temperature down to normal for a period of 30-33 d. Naproxen had the most rapid effect. In cases of fever relapse with the first drug, when the other two drugs were given instead, both proved equally effective. No side-effects were observed. We conclude that Naproxen, Indomethacin and Diclophenac sodium are equally effective in ameliorating paraneoplastic fever. In relapse, a second drug given subsequently can be effective as well. 