Using a representative sample of 5028 dentulous Finnish adults the occurrence of periodontal pockets was studied separately for the maxillae and the mandibles among removable partial denture (RPD) wearers and non-wearers. RPD(s) were worn in 11.2% of the 3444 maxillae with at least four natural teeth remaining, and in 7.7% of the 4706 corresponding mandibles (P less than 0.001). Periodontal pockets were more frequently observed in maxillae than mandibles. Wearing of RPDs highly significantly (P less than 0.0001) increased the odds of having periodontal pockets in general (4 mm or more) as well as the odds of having deeper periodontal pockets (exceeding 6 mm). This phenomenon was observed both in the maxillae and in the mandibles. These results suggest that wearing of RPD is a threat to periodontal tissues and that dentists should take care to frequently recall their patients fitted with RPD(s). During the recall visits more attention should be paid to the periodontal conditions of patients wearing RPD(s).