To examine whether antipyretic therapy in young children is associated with potential risks (interference with enhanced host defences at febrile temperatures) or benefits (improved comfort and behaviour), a randomised, double-blind, placebo-controlled trial of paracetamol was conducted among 225 children 6 months to 6 years of age who presented with acute (less than or equal to 4 days) fever (greater than or equal to 38 degrees C per rectum) without evident bacterial focus of infection. Parents were asked to give paracetamol liquid 10-15 mg/kg or placebo every 4 h as needed for fever and to avoid bathing, sponging, or other pharmacological agents. Parents kept temperature and symptom diaries and recorded changes in child comfort and behaviour according to a pretested, 5-category Likert-type questionnaire 1-2 h after every dose. There were no significant differences between treated and placebo groups in mean duration of subsequent fever (34.7 vs 36.1 h) or other symptoms (72.9 vs 71.7 h). Paracetamol-treated children were more likely to be rated by their parents as having at least a 1-category improvement in activity (38 vs 11%; p = 0.005) and alertness (33 vs 12%; p = 0.036) but no significant differences were noted in mood, comfort, appetite, or fluid intake. That overall improvement in behaviour and comfort with paracetamol was not impressive is underscored by the inaccuracy of parents' "guess" at the end of the trial as to which agent their child had received-45% correct guesses for paracetamol and 52% for placebo. The data suggest that the clinically relevant hazards and benefits of paracetamol antipyresis have been exaggerated.