n-Docosanol has been shown to have antiviral activity. To demonstrate the efficacy of n-docosanol 10% cream in the treatment of recurrent herpes labialis, a randomised, double-blind, parallel group, placebo-controlled study was undertaken in 63 patients. In a crossover extension, 22 of the patients used the alternative treatment for a further episode. A total of 98 episodes were evaluated. Application of n-docosanol 10% cream early in the prodromal or erythema stage of a recurrent episode of herpes labialis shortened mean healing time by approximately 3 days, as compared to late treatment with n-docosanol 10% cream and early or late treatment with the placebo. The crossover study revealed that late treatment with n-docosanol 10% cream significantly reduced mean healing time compared to placebo. Treatments were well tolerated.