Considerable information exists on the changing pattern of dental caries over the last two decades, however, little longitudinal information exists on changes in the pattern of periodontal diseases. This study measured the prevalence and severity of periodontal conditions in a sample of adults from Melbourne, Australia. Data were recorded by a small team of calibrated examiners for 200 subjects who were examined in 1985, re-examined in 1990, then successfully matched. The prevalence and severity of periodontal conditions decreased in subjects over the five-year study period. Over all sites, bleeding decreased from 51.2 per cent of sites examined in 1985 to 41.9 per cent of sites examined in 1990. The proportion of sites with attachment loss of 6 mm or more, decreased from 6.9 per cent to 3.2 per cent over the five-year period. In 1985, 25.6 per cent of sites had a CPITN score of 0, in 1990, 39.8 per cent of subjects presented with the same score. Notwithstanding the limitations of the measurement parameters used in the study, on average, the adult periodontal health of the sample suggested a trend to improvement over the five-year period.