Periodonta bacteria might be involved in the etiology of rheumatic diseases. Synovial Fluid obtained from individuals with rheumatic diseases and controls was analyzed for the presence of DNA ofA. actinomycetemcomitans, P. gingivalis, P. intermedia, T. forsythia and T. denticola. DNA from synovial fluid of patients suffering from rheumatoid arthritis, psoriasisarthritis, ankylosingspondylitis and monarthritis was isolated. Subgingival bacterial colonization was analyzed at the same time. DNA fromP. gingivalis was detected more of ten in syovial fluid of patients with rheumatic diseases than in controls. In morepatientswithrheumaticdiseases DNA of P. gingivalis was detected in both, oral plaque and syovial fluid. Periodontal parameters like missing teeth and approximal plaque index were correlated with the number of joints affected by RA. DNA of periodontopathogens can reach synovial fluid and the oral infection with P. gingivalis could be a riskfactor for rheumatic diseases.