The aim of the study was to examine frequency and distribution of etiologic factors which, associated with chronic inflammation, can influence the forming of intrabony periodontal defects. The following were studied: occlusal trauma, erosions and concrements on the roots, tooth malposition, the absence of contact point, inadequate interproximal distance of roots and iatrogenic factors. The results revealed that the most frequent etiologic factor in the forming of intrabony periodontal defects was occlusal trauma--55.8%, erosion of the roots--38% and concrements in the roots--34%, as tooth malposition, inadequate interproximal distances of the roots, the absence of contact point and iatrogenic factors. In the forming of 23.5% of intrabony periodontal defects two or more of the studied factors pariticipated. By the analysis of the distribution of etiologic factors by jaw segments, it was concluded that occlusal trauma was the most frequent in upper incisors--61.6%. In upper premolars the most frequent factor was the erosion on the roots--75%, and in the upper molars iatrogenic factors and erosion of the roots--44.4%. In the lower incisors, occlusal trauma was the most frequent--62.5%, in premolars also trauma--35.7%, and concrements of the molars--64.2%. Considering the high incidence the factors associated with chronic inflammation can be extremely significant in the forming of intrabony periodontal defects during parodontopahty.