The interleukin-4 receptor (IL-4R) can bind both, IL-4 and IL-13. Then T-cells were stimulated to differentiate to Th2-cells which promote B-cell proliferation and antibody production. The 1902 A/G polymorphism of the gene encoded for the α chain of the interleukin-4 receptor (IL-4RA) was found associated with enhanced IL-4 receptor activity. Therefore, the aim of this study was to evaluate putative associations of this polymorphism to generalized aggressive or chronic periodontitis and five periodontopathogens. Methods: 120 patients with severe generalized periodontitis (attachment loss >6mm in >35% of the teeth, chronic periodontitis: n=53, mean age=48.9±9.8 years; aggressive periodontitis: n=67, mean age=41±9.9 years) in comparison to periodontitis free controls (n=81, mean age=46.9±10.7 years). Interleukin-4RA polymorphism was analyzed by PCR-SSP (CTS-Kit, Heidelberg). Distributions of single alleles and genotypes were calculated by Chi²-Test with Yates correction or Fisher's exact test. Subgingival bacteria were analyzed molecular biologically using micro-Ident® test (HainLifescience, Nehren). Adjusted odds ratios were determined by logistic regression with respect to established cofactors for periodontitis such as age, gender, smoking status, and plaque index. Results: The mutant allele IL-4RA 1902 G (28.3% vs. 17%, p=0.041) and the mutant genotypes GA+GG (50.9% vs. 29.6%, p=0.021) occurred more frequently in patients with chronic periodontitis. The latter association could be confirmed by logistic regression analysis (OR=2.1, 95%CI 1.2-4.0, p=0.016). In the total study cohort the genotypes GA+GG were positive associated to the presence of T. forsythia (88.9% vs. 76.75%, p=0.045). This result remained significant after logistic regression (OR=1.5 95%CI 1.2-1.9, p= 0.001). Conclusions: The IL-4RA 1902 AG polymorphism is a putative risk indicator for generalized chronic periodontitis and the subgingival occurrence of T. fosythia. Schlagwörter: IL-4 receptor alpha, polymorphism, chronic periodontitis, aggressive periodontitis