Background: One in eight schoolchildren have an episode of acute infective con junctivitis every year. Standard clinical practice is to prescribe a topical ant ibiotic, although the evidence to support this practice is scarce. We undertook a randomised double-blind trial to compare the effectiveness of chloramphenicol eye drops with placebo in children with infective conjunctivitis in primary care. Methods: Our study included 326 children aged 6 months to 12 years with a clinical diagnosis of conjunctivitis who were recruite d from 12 general medical practices in the UK. We assigned 163 children to recei ve chloramphenicol eye drops and 163 to receive placebo eye drops. Eye swabs wer e taken for bacterial and viral analysis. The primary outcome was clinical cure at day 7, which was assessed from diaries completed by parents. All children wer e followed up for 6 weeks to identify relapse. Survival statistics were used for comparison, and analysis was by intention to treat. Findings: Nine children wer e lost to follow-up (one in chloramphenicol group; eight in placebo group). Cli nical cure by day 7 occurred in 128 (83%) of 155 children with placebo compared with 140 (86%) of 162 with chloramphenicol (risk difference 3.8%, 95%CI-4.1 %to 11.8%). Seven (4%) children with chloramphenicol and five (3%) with plac ebo had further conjunctivitis episodes within 6 weeks (1.2%,-2.9%to 5.3%). Adverse events were rare and evenly distributed between each group. Interpretati on: Most children presenting with acute infective conjunctivitis in primary care will get better by themselves and do not need treatment with an antibiotic. Background: One in eight schoolchildren have an episode of acute infective con junctivitis every year. The standard clinical practice is to prescribe a topical ant ibiotic, although the evidence to support this practice is scarce. We undertook a randomized double-blind trial to compare the effectiveness of chloramphenicol eye drops with placebo in children with infective conjunctivitis in primary care. Methods: Our study included 326 children aged 6 months to 12 years with a clinical diagnosis of conjunctivitis who were recruite d from 12 general medical practices in the UK. We assigned 163 Eye to swabs wer e taken for bacterial and viral analysis. The primary outcome was clinical cure at day 7, which was assessed from diaries completed by parents. All children wer e followed up for 6 weeks to identify relapse. Survival statistics were used for comparison, and analysis was by intention to treat. Findings: Nin e children wer e lost to follow-up (one in chloramphenicol group; eight in placebo group). Cli nical cure by day 7 occurred in 128 (83%) of 155 children with placebo compared with 140 (86%) of 162 with chloramphenicol Seven (4%) children with chloramphenicol and five (3%) with plac ebo had more conjunctivitis episodes within 6 weeks (1.2%, -2.9% to 5.3 %). Adverse events were rare and evenly distributed between each group. Interpretati on: Most children presenting with acute infective conjunctivitis in primary care will get better by themselves and do not need need treatment with an antibiotic.