The oral antiviral valacyclovir, which is 3 to 5 times more bioavailable than its parent compound acyclovir, is a good candidate for effective therapy to suppress recurrent herpes labialis lesions. The efficacy of oral valacyclovir in the suppression of herpes labialis has not previously been reported. Two identical, randomized, double-blind, parallel-group studies were conducted to evaluate the efficacy of oral valacyclovir 500 mg (n=49) versus placebo (n=49) once daily for 16 weeks in the suppression of herpes labialis among patients with a history of 4 or more recurrent lesions in the previous year. Data from the studies were pooled for analysis. Twenty-eight patients (60%) in the valacyclovir group compared with only 18 patients (38%) in the placebo group were recurrence-free throughout the 4-month treatment period (P=.041). The mean time to first recurrence was significantly longer with valacyclovir (13.1 weeks) compared with placebo (9.6 weeks)(P=.016). The total number of recurrences in patients using valacyclovir was 24 compared with 41 in patients using placebo. The incidence of adverse events during the 4-month treatment period was slightly lower in the valacyclovir group (22 events, 33% of patients) compared with the placebo group (29 events, 39% of patients). The results of these small double-blind, placebo-controlled studies suggest that oral valacyclovir 500 mg once daily for 4 months is effective and well tolerated for the prevention of recurrent herpes labialis. More research with larger patient numbers is warranted to corroborate and extend these findings.