The second-generation macrolide azithromycin is available as a 1.5% ophthalmic solution for use in the treatment of bacterial or trachomatous conjunctivitis. This article reviews the pharmacological properties of azithromycin 1.5% ophthalmic solution and its clinical efficacy and tolerability in patients with purulent bacterial conjunctivitis or trachomatous conjunctivitis caused by Chlamydia trachomatis. Azithromycin 1.5% ophthalmic solution had good in vitro activity against Haemophilus influenzae and C. trachomatis, and achieved good concentrations in tear samples from healthy volunteers. Azithromycin 1.5% ophthalmic solution for 3 days (1 drop twice daily) was noninferior to tobramycin 0.3% ophthalmic solution for 7 days (1 drop every 2 hours) in paediatric and adult patients with purulent bacterial conjunctivitis, with regard to clinical cure and bacteriological resolution on day 9, in a randomized, investigator-masked, multicentre study. In children with trachomatous inflammation, 3-day treatment with azithromycin 1.5% ophthalmic solution was noninferior to a single dose of azithromycin oral suspension, with regard to clinical cure rate in the worst eye at 60 days, in a randomized, double-masked, multicentre study. Azithromycin 1.5% ophthalmic solution was well tolerated in patients with bacterial or trachomatous conjunctivitis. Most events were of mild to moderate severity.