191 subjects, aged 35-80 years, were examined for periodontal disease using radiographic and clinical means. At all approximal tooth surfaces, assessments were made of (i) the distance on radiographs between the cementoenamel junction and the most coronal level of the alveolar bone, and (ii) probing attachment loss. The results revealed that (i) a strong correlation existed between the radiographic and the clinical assessments (r = 0.80, p = 0.0001), (ii) the difference between the 2 types of assessments was within 2 mm in 92% of the tooth sites examined, (iii) the degree of agreement between the 2 methods was similar, irrespective of tooth type and tooth surface, but (iv) the agreement was poor at sites with severe periodontal tissue breakdown.