Forty patients with CIN were treated with CO2 laser. CIN consists of 14 mild dysplasia, 10 moderate dysplasia, 12 severe dysplasia, and 4 carcinoma in situ. The ages of the patients ranged from 26 to 50 years. CO2 Surgical Laser, System 400, was used, and most of laser therapy was administered with continuous, defocused beam under 25 watts power. The periods of follow up were from 3 to 22 months, 29 patients followed more than 6 months. All of the patients are in remission at present. Three out of 14 mild dysplasia and 1 out of 12 severe dysplasia needed the second treatment because of persistence. All persistent diseases were found within 7 weeks after the initial treatment. These patients were treated with lower power in the earlier period of this study. All the patients were treated at the outpatient without anesthesia. The patients felt mild pains and/or heat sensation in the lower abdomen, but none of them needed analgesia. CO2 laser seems to be an effective armamentarium for the treatment of CIN.