The aim of this study was to assess the prevalence and severity of periodontal destruction in regular dental attenders in Northern Ireland. 132 individuals aged between 20 and 49 years who had recently had a course of routine treatment in the General Dental Service completed a questionnaire and had a periodontal examination. Measurements of plaque, subgingival calculus, bleeding, probing pocket depth and periodontal attachment level were made at 4 proximal sites per tooth. Plaque was present at an average of 17%, subgingival calculus at 13%, and bleeding on probing at 34% of interproximal surfaces examined. The mean probing pocket depth was 2.7 mm and the mean probing attachment level was 1.0 mm. Incipient periodontal destruction was common with all subjects having at least 1 pocket of greater than or equal to 3 mm and 90% having at least 1 site with greater than or equal to 2 mm attachment loss. Only 24 (18%) of those examined had deep pocketing or severe loss of periodontal attachment (greater than or equal to 6 mm). The extent of deep pocketing and severe attachment loss was low at only 0.2% and 0.6%, respectively, of the sites examined. It was concluded that gingivitis and incipient periodontitis were prevalent and extensive in the regular dental attenders investigated, but that severe periodontal destruction was uncommon.