Objective To evaluate clinical outcomes, patient satisfaction, and maintenance after treatment from mandibular implant-supported overdentures with different attachment types. Methods We searched six electronic databases: the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 4, 2005), Current Controlled Trials, MEDLINE (1966 to Sept. 2005), EMBASE (1984 to Sept. 2005), and Chinese biomedical database disk (1978 to Sept. 2005). Eleven Chinese professional journals in oral health were also handsearched from their first published issues. Three authors screened and selected the studies, appraised their methodological quality and extracted data from the studies. The results were presented narratively by meta-analysis. Results After strict screening, 12 trials involving 282 patients were included. Two of the trials were included in a meta-analysis with 27 patients in bar-clip group, 29 patients in ball-spring group, and the other trials were described thoroughly. The findings seemed to indicate that the bar-clip group had the highest retention but more oral mucosa complications, while the ball-spring group had good retention and less oral mucosa complications but needed more aftercare treatments, and the magnetic group had less retention but better peri-implant outcomes. Conclusions There is inadequate evidence to prove which is the best choice for mandibular implant-supported overdentures among bar-clip, ball-spring and magnetic attachments. More controlled clinical trials are required to guide clinicians on the choice of the type of attachment in mandibular implant-supported overdenture.