A total of 122 patients presenting with acute ankle injuries within 6 h of injury were entered into a double-blind study. Treatment consisted of a standardized regimen of physiotherapy and elastic support for all patients, who were then randomized into two groups. One group received immediate ibuprofen (2400 mg/day) while the other group received placebo medication for 48 h, followed by ibuprofen (2400 mg/day) from the 3rd day onwards, i.e. delayed antiinflammatory treatment. Assessments were made by means of a daily diary and also by clinical and radiological examination. The immediate treatment group demonstrated more rapid recovery by day 7 in terms of regression of swelling (P less than 0.01) and clinician's impression of severity (P less than 0.05). This group also tended to consider their ankle more able to bear weight at this stage (P = 0.05). In comparison with an earlier study, in which the only active treatment was an elastic support, a greater percentage of patients recovered earlier in the present study. The incidence of side-effects was low. Immediate high-dose ibuprofen is therefore recommended as treatment for moderate to severe acute ankle injuries.