Purpose: The purpose of this study was to compare between two different impression techniques in ball and socket attachments supported complete implant overdentures on electromyographic activity. Material and Methods: Ten fully edentulous patients were chosen from the patient clinic of removable prosthodontics department, Patients were divided into 2 groups according to the type of impression technique Group 1: The patients received the denture with the open impression tray technique then a washing period of two weeks elapsed and then switched to the other denture with closed impression tray technique. Group 2: The patients received the denture with the closed impression tray technique then washing period of two weeks elapsed and then switched to the other denture with open tray impression technique. Electromyographic activity measurements were made when the patient in each group wear dentures for one month then a wash out period for two weeks and once more measurements were made when the patient wear the other denture respectively. Masticatory efficiency and electromyographic activity were tested. Results: Patients received dentures made with closed tray impression techniques showed higher masticatory efficiency and lower electromyographic activity than patients received dentures with open tray impression techniques during chewing hard food so significant difference between two techniques were calculated. Conclusions: From the findings of this study; it was concluded that: 1-Masticatory efficiency improved and also the electromyographic activity decreased in patients using closed tray impression technique than that with open tray impression technique during chewing hard food