In an open-label study, the concentrations of azithromycin in middle ear effusions and plasma were determined in 29 children between 1 and 8 years of age with a diagnosis of either secretory otitis media of at least 1 month's duration or acute otitis media. Azithromycin (10 mg/kg) was administered as a single dose 12, 24 or 48 h before the insertion of tympanostomy tubes to 17 children with secretory otitis media and once daily for 5 days (10 mg/kg on day 1, 5 mg/kg on days 2-5) to 12 children with acute otitis media. In the 16 evaluable patients with secretory otitis media, azithromycin penetrated middle ear effusions, with group mean concentrations approximately two orders of magnitude greater than the concurrent plasma concentrations 12, 24 and 48 h after administration. Similar plasma:effusion ratios were found 24 and 48 h after starting once-daily therapy in 10 evaluable patients with acute otitis media.