The authors report the results of a randomised, multi-centric study comparing the antipyretic activity of tiaprofenic acid to that of acetaminophen. Seventy nine children of both sexes, aged 8 months to 9 years, having an average temperature at inclusion of 38.5 degrees C (+/- 0.5 degree C), received as a single dose 50 mg of tiaprofenic acid (3.7 +/- 0.9 mg/kg) (40 children) or 100 mg of acetaminophen (7.7 +/- 1.7 mg/kg) (39 children) for upper respiratory tract infection. The rectal temperature was taken regularly over a 6-hour period. Whatever the criteria considered (gradient between the initial temperature and the lowest temperature observed, difference of temperature at the different time points between the two groups), tiaprofenic acid appeared as effective an antipyretic as acetaminophen. Tolerance was good in both groups. Tiaprofenic acid appears as an interesting alternative to acetaminophen in the treatment of fever in upper respiratory tract infections in children.