The purpose of this study was to determine the presence of suspected periodontal pathogens in the peri-implant microflora of osseointegrated implants exposed 3 and 6 months to the oral environment of patients previously treated for periodontal disease. Subgingival microbial samples were taken in the deepest residual pocket of each quadrant in 10 patients before placement of ITI implants and in 10 patients before abutment connection of Brånemark implants. The samples were cultured using continuous anaerobic techniques. 4 patients were positive for P. gingivalis, 13 for P. intermedia, 2 for A. actinomycetemcomitans, 16 for Fusobacterium, 7 for C. rectus and 12 showed microscopic evidence of spirochetes. After 3 and 6 months exposure of the implants to the oral environment, one sample was obtained from the peri-implant sulcus in each patient. P. gingivalis was found in 2 patients in the peri-implant samples after 3 and 6 months. 6 peri-implant samples were positive for P. intermedia after 3 months, 7 after 6 months. Fusobacterium was present in 13 peri-implant samples after 3, and in 12 samples after 6 months. 4 patients showed evidence of for C. rectus after 3 months, 2 after 6 months. Spirochetes were seen in 3 peri-implant samples after 3 and in 5 after 6 months. None of the implants were found to be colonized by A. actinomycetemcomitans, although the organism was detected on teeth in 1 individual. Similar distribution patterns were noted for ITI and Brånemark type implants.(ABSTRACT TRUNCATED AT 250 WORDS)