Objectives: Our previous studies revealed certain single HLA markers, HLA homozygosities, heterozygosities and combinations which were positively or negatively associated with aggressive (AP) or chronic periodontitis (CP). Due to bacterial mimicry with HLA and HLA-dependent immunoreactivity to bacterial antigens a similar association with periodontopathic bacteria could be assumed. Therefore, the aim of the present study was to evaluate HLA associations to A. actinomycetemcomitans (A.a.), P. gingivalis (P.g.), P. intermedia (P.i.), T. forsythensis (T.f.) and T. denticola (T.d.) in patients with AP (N = 33, age 37 years, females 57,6 %) and patients with CP (N = 35, age 47 years, females 62,9 %). Methods: In both patient groups the smoking status, the approximal plaque index (API), bleeding on probing (BOP) and the clinical attachment loss (CAL) were determined. Bacterial infection was analyzed employing a PCR-rSSO microDent DNA-Strip technique (Hain Lifescience GmbH, Nehren, Germany). HLA-A, -B, -Cw, -DR, -DQ typing was performed by both CDC (Complement Depending Cytotoxicity assay, BAG, Lich, Germany) and polymerase chain reaction with sequence-specific primers (PCR-SSP, GenoVision VertriebsmbH Schwechat, Austria). Statistical calculations were carried out by Chi²-testing, with Yates correction or Fishers Exact test, if appropriate, and determination of Pearson`s correlation coefficient (r). Results: The occurence of an A.a. infection was found to be positively associated with the haplotypes HLA-B*08:Cw*07:DRB1*03:DRB3*(DR52):DQB1*02 as well as HLA-DRB1*13:DRB3*:DQB1*06, whereas a negative association was found to HLA-DRB1*04:DRB4*:DQB1*03. HLA-A*02 positve patients were always infected with P.g.. An infection with P.i. occurred less frequent in patients expressing HLA-B*5, HLA-DRB1*13, -B*44:DRB1*13 or -DRB1*13:DRB3*(DR52):DQB1*06. T.f. was negatively associated with HLA-A*33. Conclusions: Single HLA markers and HLA combinations appear to influence the susceptibility for an infection with periodontopathic bacteria. In this context, it may be of interest that both HLA-B*08 and HLA-DRB1*04:DRB4*(DR53) positive haplotypes are also associated with several other chronic inflammatory or autoimmune diseases.