Aim: To evaluate the efficacy of Rotary Files Protaper in root canal preparation. Objectives and Methods: A follow-up study with 50 molars and premolars were prepared using Rotary Files Protaper, crowndown technique. Total time for shaping root canals, shape of prepared canals, length obturation, resulting treatment after 1 week and 6 months were evaluated. Results: Average time to prepare root canal is 31.57 + or - 12.96 minuts at molars and 11.46 + or - 6.62 minuts at premolars. 98 percent has a tapering conical root canal form, 42 percent need 1 time treatment, no patient need 3 time over, 90.0 percent good length root canal preparation, 94 percent has no symptpm after obturation, the success rate after 6 monhs is 95.6 percent. Conclusion: Root canal preparation with Rotary Files Protaper Protaper fastly, less time, shape a continuously tapering conical root canal form which help the treatment of root canals is easier and safer, the success rate is higher.