Purpose: To compare the effect of open field versus closed field magnetic attachments used to retain two teeth supported mandibular overdenture. Materials and Methods: Twelve patients were selected having completely edentulous maxilla and two remaining mandibular canines. According to the type of magnet, patients were classified into 2 equal groups; group I used open field magnet and group II used closed field magnet. Clinical and radiographic evaluation were carried out at time of insertion(T0), 6 months(T1), 12 months(T2)  and 18 months (T3) after insertion. Clinical evaluation included probing depth, plaque index and bleeding index. Radiographic evaluation through periapical parallel x-ray technique .Retention measurements were carried out 4 weeks after denture settlement.. Results:There were statistically significant differences between the two groups regarding plaque score at T3, probing score at T1, T2, and T3, and bleeding score at T1, radiographic bone level changes at T1, T2, T3, T4 and retention values between the two groups. While there was no significant difference regarding plaque score at T0, T1, and T2, probing score at T0, and bleeding score at T1, T2, and T3. Conclusion:On the light of the study, closed field magnet provided relatively higher retentive forces than opened field magnets. Closed field magnet was found to be superior to opened field based on clinical and radiographic evaluation. Key words:tooth supported overdenture, open field magnet, closed field magnet.