DNA probes are commonly used for improvement of periodontal diagnosis. In this present study, two simultaneously collected periodontal plaque samples were analyzed by two commercially available DNA probes (IAI PadoTest 4.5® and microDent®). The aim of this study was to compare the results of these tests and to determine their degree of correspondence. In the first investigation, samples from 20 sites (10 sites each) were analyzed by each test. The percentage of corresponding sites in which both samples were tested positively are as follows (IAI PadoTest 4·5® / microDent®): A.a. 100%/ 100%, B.f. 70%/ 90%, P.g. 90%/ 100% and T.d. 60%/ 90%. In a second investigation, a total of 271 plaque samples were analyzed by both tests. The results also displayed a high correspondence between the two tests: A.a. 82,6%, B.f. 76,6%, P.g. 80% and T.d. 67,4%. Thus it can be concluded that the results of both tests are well corresponding concerning the pathogens A.a., B.f., P.g. and T.d. The results did not show any clear superiority for any one of the tests. Nevertheless, the results of the second investigation give reason to carefully interpret results from DNA probe tests. Treatment planning should therefor not be based on test results alone, but additionally on good clinical judgement. Keywords: Parodontitis, DNA-Sonden, Mikrobiologie, Diagnostik