Objectives: This study aimed to investigate masticatory muscle activity in patients treated with2 modalities of implant mandibular overdenture prosthesis.Methodology: Fourteen completely edentulous male patients were selected and four implantswere inserted for each patient. After 3 months of installation, the patients were equally divided intotwo groups; group I receiving overdentures retained with ball attachments and group II receivingtelescopic retained overdentures. Muscle activity was measured at time of denture insertion, twoweeks and one month after insertion.Results: The results revealed that muscle activity was significantly lower in telescopic retainedoverdentures compared to overdentures retained with ball attachments.Conclusion: Telescopic attachments decreased the effort exerted by the muscles compared toball and socket attachments.