Primary symptomatic herpes simplex virus infection in children usually manifests as gingivostomatitis and is prevalent in the 1- to 3-year age group. The disease involves the buccal and gingival mucosa and the tongue, and lasts approximately 2 weeks. Two recent non-blind studies reported a more rapid regression of symptoms after treatment with aciclovir suspension. Three randomised double-blind, placebo-controlled trials have clearly demonstrated that early aciclovir treatment significantly shortens the duration of all clinical manifestations and infectivity of affected children compared with placebo. We conclude that the treatment of herpetic gingivostomatitis with aciclovir is recommended. Treatment should be started within the first 3 days of disease onset. The proposed therapeutic dose is 15 mg/kg, 5 times daily for 5 to 7 days.