The aim of this study was to compare the effect of location and number of implants on the retention and stability of magnetically retained mandibular overdentures. Four groups of such prostheses were classified according to number and position of the implants in the canine, premolar, or molar regions. Significant differences in retention were observed when 6 magnets were used (4.66 ± 0.45 N), whereas the lowest retention was obtained with 2 magnets (2.1 ± 0.43 N). Only oblique stability was improved significantly when the number of implants was increased.