OBJECTIVE To evaluate arthroscopic versus fluoroscopic reduction and percutaneous fixation of lateral tibial plateau fractures of AO/OTA Types 41.B1 to 41.B3. METHODS Prospective study. METHODS University hospital. METHODS One hundred sixty-eight patients underwent operative treatment for a tibial plateau fracture from 1988 to 1995. Thirty-three of these patients had monocondylar fractures of the lateral plateau that were treated by percutaneous reduction and fixation techniques. In the first ten cases, arthroscopic control of reduction was used. The following twenty-three consecutive cases were treated by reduction and fixation solely under fluoroscopic control. The arthroscopy group was followed for a mean of fifty-two months and the fluoroscopy group for thirty-eight months. RESULTS Nine of ten cases of the arthroscopy group had an excellent or good result in Rasmussen's knee score at follow-up. One patient with an unreduced anterolateral depression zone despite arthroscopic surgery required a total knee prosthesis after eighteen months. Sixteen cases in the fluoroscopy group met the follow-up criteria. Fifteen were graded good or excellent in Rasmussen's clinical score; sixteen were excellent or good in the radiological score. One patient claimed chronic medial joint line pain after a lateral split fracture and had arthroscopy revealing chondral degeneration on the medial side but had no pathological findings in the lateral compartment. No secondary meniscus or ligament surgery was performed in the follow-up period. CONCLUSIONS Percutaneous treatment of fractures of the tibial plateau can be performed using arthroscopy as well as image intensification to control reduction of the joint surface. We were not able to demonstrate any significant benefit from arthroscopy compared with fluoroscopic reduction. Reduction under image intensification is technically easier in our practice, especially in serial fractures and multiply injured patients. We reserve arthroscopy for cases with significant ligament injuries and for children with fractures of the median eminence.