In a double-blind, multicentre trial, 382 patients with a diagnosis of acute purulent sinusitis were randomised to receive sparfloxacin 200 mg once daily for 5 days following a loading dose of 400 mg on day 1 (n = 193) or cefuroxime axetil 250 mg twice daily for 8 days (n = 189). Patients were classified as success or failure according to clinical symptoms plus bacteriological and radiological data at the end of treatment and at a follow-up visit. In analyses of the intent-to-treat (n = 374) and evaluable populations (n = 304), the 5 day course of sparfloxacin was at least as effective and well tolerated as the 8 day course of cefuroxime axetil. The success rates at the end of treatment in the evaluable population were 82.6% and 83.2% in the sparfloxacin and cefuroxime axetil groups, respectively. The pathogens isolated most frequently were Haemophilus influenzae (33%) and Streptococcus pneumoniae (28%). Response rates according to the bacterial aetiology of the acute sinusitis were similar in the two treatment groups. Both drugs were well tolerated. The commonest adverse events were gastrointestinal and were reported in 2.6% and 3.8% of sparfloxacin- and cefuroxime axetil-treated patients, respectively.