The aim of this study was to investigate the prevalence and extent of periodontal disease registered as marginal bone loss and subject characteristics in the adult population in the county of Skåne in Sweden. One thousand individuals, 20-89 years old, were randomly selected and 451 subjects agreed to participate in the study. They answered a questionnaire and in conjunction with the clinical and radiological examination the subjects answered questions about their medical history. The examiners were co-ordinated regarding the diagnostic criteria through comprehensive written instructions, practice and discussions of clinical cases. One observer estimated marginal bone loss around the teeth on digital panoramic radiographs and bitewings. The individuals were classified regarding periodontal disease experience according to the following criteria: PD- = loss of supporting bone tissue or = 1/3 of the root length in or = 1/3 the root length in > or = 30% of the teeth. Subjects with no or minor bone loss, i.e. PD- constituted 69% of the population. Twenty percent of the study population had marginal bone loss corresponding to localised periodontal disease (PD) and 11% exhibited generalised periodontal bone loss (PD+). The periodontal treatment need, defined as probing pocket depth > or = 6 mm and bleeding on probing > or = 20%, was 53% in the PD+ group. An interesting result was that there were no differences in periodontal disease experience between the genders.The prevalence and extent of periodontal disease in this study correlates well with recent other studies. Eleven percent of the population has experienced generalised periodontal disease, and 53% of them have a periodontal treatment need defined as 1 or more site with PPD > or = 6 mm and BoP > or = 20%.