Purpose: the purpose of this investigationwas toprovide within subjects clinical evaluation of the effect of implant number and  location on the magnitude of force required to dislodge mandibular overdenture and the bite force clinically  in the lateral incisors, canine areas and both. Materials and Methods: six completely edentulous patients were selected for this study.Each patient received two implants in the lateral incisors and the other two implants were installed in the canine areas bilaterally. The bite force and clinical retention were measured after one week of denture insertion in lateralincisors , canine areas and both. Results:For all inserts, the highest retention was noted with four implant overdentures, followed by two canine implant overdentures and the lowest retention was noted with two lateral incisor implant overdentures except for orange insert which recorded non significant difference between lateral incisors and canine positions.For each implant position, blue inserts recorded significant higher retention forces than off-white and orange inserts. For all inserts, the highest bite forces were noted with four implant overdentures which recorded significant difference compared to two lateral incisors and two canine implants while there was non-significant difference between two incisor and two canine positions. For each implant position , blue insert recorded significant higher bite forces than orange and off-white inserts while there was non significant difference between off-white and orange inserts. Conclusion: The four implant supported overdenture was the best regardingretention and bite force. The most favorable position of two implants retaining mandibular overdenture with blue and off white positioner attachments wascanine position as it was associated with increased initial  clinical retention while the bite force was not affected by implant position. Blue insert was higher than off-white and orange inserts regardinginitial clinical retention and bite force. Key words: implant overdenture, positioner, four implants