PURPOSE: To evaluate the efficacy and the toxicity of 0.15% ganciclovir gel in the treatment of adenoviral conjunctivitis and in preventing ocular complications after adenoviral conjunctivitis, such as corneal infiltrates and pseudomembranes. METHODS: Double blind, interventional and randomized clinical trial. Thirty-three patients with clinical diagnosis of adenoviral conjunctivitis with onset of symptoms for five or less days were randomized in two groups: Group 1 (treatment) with 19 patients used ganciclovir gel and Group 2 (control) with 14 patients used artificial tears without preservative. Patients answered a questionnaire of signs and symptoms and were submitted to an ophthalmologic exam. On the 6th and 10th days of treatment they answered the same questions and were re-examined by the same ophthalmologist. Signs and symptoms were compared. T Student, Mann-Whitney e Wilcoxon tests were used to statistical analysis. RESULTS: Trend of better response in the treatment group in relation of patients' perception, besides faster improvement of this group compared to the control group (p=0.26). There were lower transmission to the fellow eye (p=0.86) and to people living together (p=0.16) in the treatment group. No statistical difference related to signs and symptoms of conjunctivitis were found comparing both groups. We observed statistical difference in pain, itch and photophobia only in the treatment group, comparing each group alone. No toxicity and more tolerance of the ganciclovir were observed. There was no statistical difference in the ocular complications after conjunctivitis between both groups. CONCLUSIONS: This study showed trend of better and faster response of the signs and symptoms of the patients treated with ganciclovir compared with the control group, but with no statistical significant. These results need to be confirmed by additional studies, with more patients and longer follow-up. Clinical Trails.gov: NCT01349452.