In a double-blind, randomised, placebo-controlled trial of intravenous acyclovir (ACV) in normal adults with chickenpox, the drug was shown to have a significant effect on the duration of vesicles, on virus counts after one day's treatment and in lowering the body temperature on the third, fourth and sixth days of treatment. There were no significant effects on the duration of symptoms or on the evolution of the rash. No adverse effects of acyclovir were seen.