The influence of end abutment and cantilever fixed partial dentures on periodontal health was examined in 12 patients with periodontally reduced residual dentition. The prosthetic appliances had been integrated for 4 to 6 years before the first follow-up examination and had no technical defects at baseline. Two follow-up examinations were performed at a 12-month interval to record clinical and microbiologic parameters of 62 abutment teeth, 45 of which were fitted with end abutment fixed partial dentures and 17 with cantilever fixed partial dentures. Both types of fixed partial dentures were represented in all patients. The patients were on a 6 to 8-week recall schedule throughout the study period and had good oral hygiene. At both examinations, subgingival plaque samples were taken at all proximal surfaces and evaluated by dark-field microscopy. The clinical parameters used were Gingival Index, Plaque Index, pocket probing depth, and attachment level. The results showed that both types of fixed partial dentures were compatible with periodontal health subject to optimal oral hygiene. The clinical parameter s recorded remained stable at a very low level throughout the study period and were almost identical in both groups. A slight gain in clinical attachment level, with a mean value of 0.19 mm for abutment teeth fitted with cantilever fixed partial dentures and of 0.32 for end abutment fixed partial dentures, was registered during the study period. The composition of the subgingival plaque showed a microflora reflecting virtually health periodontal conditons. The proportion of motile rods and spirochetes was slightly elevated in both groups. In conclusion, it can be stated that both fixed partial denture t ypes display identical characteristics in the periodontally damaged dentition and do not lead to deteriorati on of the periodontal situation if oral hygiene is closely monitored.