A double-blind, randomised, parallel group study has been done comparing the efficacy and tolerability of 7.5 mg/kg ibuprofen syrup (n = 77) and 10 mg.kg-1 acetaminophen syrup (n = 77) in 154 children (6 months to 5 years) with fever (> or = 38 degrees C) associated with infectious diseases and treated with antibiotic therapy. The area under the percentage reduction in temperature curve captured the net effect of each drug and provided the best estimate for comparison of efficacy during a defined period. Temperature evolution over time was not significantly different between the two groups. Nevertheless, the temperature reduction over the first 4 h of treatment (H0-H4) was significantly higher after ibuprofen (60%) than acetaminophen (45%). Both ibuprofen and acetaminophen were well tolerated. In conclusion, significant antipyretic activity, good tolerability and its availability as a syrup make ibuprofen an effective means of fever control in children.