Periodontitis is an inflammatory disease caused by microbial infection in the subgingival region. Risk factors associated with the development and progression of this disease are numerous, multifactorial, complex, and often not well defined across individuals and population groups. The focus of this paper is to provide an overview of existing information relevant to oral hygiene and compliance as risk factors in periodontitis and to present a 26-month prospective clinical study dealing with the same. The review of literature from epidemiological, clinical, and public health perspectives indicated that oral hygiene can be considered as risk indicator, risk factor, and/or risk predictor. The extent of oral hygiene contribution to the overall risk of individuals and population varies greatly across studies. Such variations may be attributed to population, personal and disease characteristics, research methodology used, and analytical strategies employed. The purpose of the study reported was to determine the role of self-reported daily oral hygiene practices and clinical plaque scores as risk factors in a middle-aged health-conscious population with early periodontitis. The group consisted of 174 subjects selected on the basis of putative bacterial risk markers and clinical indices. Medical, dental, behavioral, and clinical periodontal measurements including plaque, calculus, gingival inflammation, probing depth, bleeding on probing, and relative attachment level were obtained by one of two calibrated examiners at baseline, 14, 20, and 26 months. Data analyses revealed that some trends were seen relevant to self-reported oral hygiene and plaque scores favoring oral hygiene as a possible risk factor in periodontitis. Such trends, however, were neither clear nor consistent across various clinical parameters and observation intervals.(ABSTRACT TRUNCATED AT 250 WORDS)