Objective: To evaluate the effect of cimetidine in relapse prevention in patients with genital warts compared with CO2 laser therapy merely. Methods: A randomized controlled clinical trial. 63 patients were divided into 2 groups: group 1: 32 patients were treated with CO2 laser in collaboration with oral cimetidine 40mg/kg/24h dose for 8 weeks, group 2: 31 patients were treated with CO2 laser. Results: The healing rate after one treatment with CO2 laser for the two groups is respectively 64.52 percent and 50 percent. Monitoring after treatment 3 months, 6 months and one year showed no relapse rate is over 80 percent, the difference in recurrence rates between the 2 groups is not statistically significant. Conclusion: Immunomodulatory role of cimetidine in the treatment of virus -' induced skin diseases, especially genital warts and common warts, have been reported. In the study, this role has not been clearly shown. May be in"the future familiar studies, the authors will clarify the contributions of cimetidine in dermatology.