This multicenter double-blind study of 157 patients was designed to evaluate the safety and efficacy of a new dosage regimen of oral acyclovir (800 mg twice a day for 5 days) for the treatment of recurrent genital herpes. The new regimen was compared with the standard dosage of 200 mg given five times a day to patients treated for three consecutive episodes (one episode with physician-initiated therapy and two with patient-initiated therapy) and followed up for three untreated episodes. The new regimen was well tolerated and effective. In male patients it may be more effective than the standard regimen of 200 mg given five times a day to treat vesicles that are already present.