The purpose of the present investigation was to examine the use of different methods of data analysis to examine the pattern of periodontal tissue destruction in a group of adults. A clinical examination was carried out on 319 subjects, 20-79 years of age, randomly selected from the population of the city of Ushiku, Japan. The following parameters were studied: missing teeth, plaque, gingivitis, probing pocket depth and probing attachment level. All surfaces of all teeth were examined. The data obtained were evaluated in 3 ways: (i) mean values for each of the clinical parameters were computed for each subject and age group, (ii) the frequency of subjects with one or more sites of attachment loss above certain thresholds was assessed, (iii) percentile plots were generated in such a way that for each age group the percent of sites in subjects with varying attachment levels could be determined. The results revealed that the subjects included in the study had poor oral hygiene, high frequency of gingivitis and loss of probing attachment which increased with age. The mean annual attachment loss for all tooth surfaces was calculated to be less than 0.1 mm. Severe periodontal tissue breakdown was not as common as might have been expected. Hence, the majority of the subjects in the 20-59 year age group had very little evidence of destructive periodontal disease. In these age groups, a comparatively small subfraction accounted for most of the disease detected. After the age of 60, periodontal disease appeared to be more widespread among the subjects examined.(ABSTRACT TRUNCATED AT 250 WORDS)