Propionibacterium sp. is commonly isolated in association with orthopedic implants, either as a pathogen or a colonizer. Microbial characteristics that indicate whether the isolated species is a likely cause of orthopedic implant infection versus a colonizing agent would be clinically useful. We performed a prospective trial to determine the species of Propionibacterium and the phylotype (IA, IB, II, III) of Propionibacterium acnes isolated from the surface of removed orthopedic implants, and we correlated these findings with the presence or absence of infection. P. acnes represented 61 of 62 isolates. P. acnes type I was more commonly isolated than was type II (62% versus 38%, respectively), whether associated with infection or not. P. acnes type III was not detected. There was no clear association between types I and II P. acnes and infection or colonization of failed orthopedic implants (P = 0.75), however type IB strains were more frequently isolated than type IA from infected prosthese.