Objectives: This study aimed to investigate masticatory muscle activity in patients treated with 2 modalities of implant mandibular overdenture prosthesis.Methodology: Fourteen completely edentulous male patients were selected and four implants were inserted for each patient. After 3 months of installation, the patients were equally divided into two groups; group I receiving overdentures retained with ball attachments and group II receiving telescopic retained overdentures. Muscle activity was measured at time of denture insertion, two weeks and one month after insertion. Results:The results revealed that muscle activity was significantly lower in telescopic retained overdentures compared to overdentures retained with ball attachments. Conclusion:Telescopic attachments decreased the effort exerted by the muscles compared to ball and socket attachments.KEY WORDS: muscular activity, implants, overdenture, telescopic attachments.(3544) Nada el khourzaty, et al.