Background: The brief period of viral replication in recurrent genital herpes lesions suggests shorter therapeutic regimens may be as effective as standard 5-day courses. Objective: To demonstrate that a 2-day course of famciclovir 500 mg statim, then 250 mg twice daily was non-inferior to the standard 5-day course of 125 mg twice daily. Methods: Patients were randomly assigned either the 2-day or 5-day famciclovir course and initiated therapy within 12 h of onset of prodromal symptoms. They were instructed to complete daily questionnaires on herpes-related symptoms and functioning and to attend the clinic for assessment of healing 5.5 days after initiating therapy. Results: A total of 873 patients were randomised at least once and 1038 recurrences were treated. The proportion of evaluable recurrences with lesions present at 5.5 days was less in the 2-day arm (24%) than in the 5-day (28%) arm. The upper 97.5% confidence limit (CL) for this difference in favour of the 2-day arm was 2% in favour of the 5-day arm, well within the 10% predefined for non-inferiority. The upper 97.5% CL was similar in the intent-to-treat, evaluable and per-protocol recurrence populations and when adjusted for baseline differences (in gender, age, herpes history and HIV infection) or for clustering of recurrences within patients. Both treatments had similar side-effects; proportion of lesions aborted; time to next recurrence; patient-reported symptoms; and impact on daily functioning. Conclusions: The 2-day course was as safe and effective as the standard 5-day course and can only enhance patient convenience and compliance.