OBJECTIVE To evaluate the analgesic activity of ibuprofen against paracetamol using a simple pain model. DESIGN A double-blind study. SETTING Twenty general practitioners in Harare, Zimbabwe. PATIENTS Adults with acute sore throat of a maximum of two days' duration. INTERVENTIONS One hundred and thirteen patients with acute pain associated with tonsillo-pharyngitis randomly received either 400 mg ibuprofen or 1000 mg paracetamol. The study design included repeated administration up to 48 hours to assess tolerability. MAIN OUTCOME MEASURES At hourly intervals for six hours after the first dose of treatment, the patients evaluated pain intensity on swallowing, difficulty in swallowing and global pain relief according to visual analogue scales. RESULTS Ibuprofen 400 mg was significantly more effective than paracetamol 1000 mg in all three ratings, at all time-points for pain intensity and difficulty in swallowing, and from two hours onwards for pain relief. There were no serious adverse effects and no statistically significant difference in the incidence of adverse effects in the two treatment groups. CONCLUSIONS Sore throat pain provided a sensitive model to assess the analgesic efficacy of class I analgesics and discriminated between the analgesic efficacy of ibuprofen and paracetamol.