The aim of this study was to evaluate the occlusal load and electromyography of patients with unilateral mandibular distal extension area treated with three designs of the removable partial denture (RPD), conventional. RPD retained by OT unilateral extra coronal attachment and RPD retained by OT cap extra coronal attachment.Material and Methods: Eighteen Kennedy class II partially edentulous patients with last second premolar is lasting abutment tooth, were selected. The patients were divided into three groups (six patients each), Group I:Received conventional RPD, which provides cross arch stabilization with a double Aker clasp on the unmodified side was fabricated. Group II;Received unilateral RPD retained by OT unilateral extra coronal attachment, Group III;Received RPD retained, by OT cap extra coronal attachment with bilateral cross arch stabilization. Evaluation of occlusal load done by using T-scanner (Digital occlusal analysis) and EMG activity done by (Electromyographic recording machine), patients of three groups were evaluated at the time of prosthesis insertion, then after 3and 6 months. Results: In the digital occlusal analysis, comparison between the three groups at the baseline, after 3 and 6 months, the better results were obtained and showed a statistically significant increase in Group II (OT unilateral), especially after 3, 6 months. Conclusion: From the results of this study, it was concluded that: The extra coronal castable precision attachment (OT unilateral) is preferred over traditional RPD and OT cap extra coronal attachment because it is easier to use, more pleasant for patients, and provides superior occlusal load distribution and better electromyographic activity.