The aim of this epidemiological study was to analyze various clinical and radiographic data on oral health and compare the results to those of three cross-sectional studies carried out in 1973 and 1983, and 1993. In 1973, 1983, 1993, and 2003 a random sample of 1,000; 1,104; 1,078; and 987 individuals, respectively, were studied. The individuals were evenly distributed in the age groups 3, 5, 10, 15, 20, 30, 40, 50, 60, 70, and 80 years. In 1973 80-year-olds were not included. All subjects were inhabitants of the City of Jönköping, Sweden. The clinical and radiographic examination assessed edentulousness, removable dentures, implants, number of teeth, caries, restorations and overhangs, oral hygiene, calculus, periodontal status, endodontic treatment, and periapical status. The number of edentulous individuals in the age groups 40-70 years was reduced from 16 per cent in 1973 to 8 per cent in 1993, and to 1 per cent in 2003. The mean number of teeth increased, and up to the age of 60 years, individuals had more or less complete dentitions. During the 30-year period,the number of carious lesions and restorations decreased in general. In the 15-year-olds the decrease in number of restored tooth surfaces was 900 per cent and the corresponding figure for 30-year-olds was 79 per cent. The age groups 60-800 years showed an increase in number of restored tooth surfaces and had as a mean 50 filled tooth surfaces. The oral health among 3-5-year-olds improved markedly between 1973 and 1993. In 2003, however, there was no further improvement in 3- and 5-year-olds compared to 1993. Generally, restorations in 2003 exhibited a high quality and 90-95 per cent had no proximal overhangs. In 1973 this figure was about 60 per cent. In the age groups 20-50 years there were continuously fewer teeth fitted with crowns or bridges during the 30-year period. In 1973 the 50-year-olds had a mean of 24.5 per cent of the teeth crowned and in 2003 6.8 percent. Compared to data from 1973 there was a reduction by half concerning occurrence of plaque and gingivitis in 2003. The frequency of individuals with one or more periodontal pockets (> or = 4 mm) increased with age. In 2003 the bone level at the age of 60 years corresponded to the bone level at the age of 40 years in 1973. The percentage of endodontically treated teeth was lower in 2003 in all age groups compared to 1973, 1983, and 1993. The percentage of endodontically treated teeth with periapical orjuxtaradicular destructions was generally lower in 2003 than in the earlier surveys, about 20 per cent in 2003 compared to 25-30 per cent in 1973,1983, and 1993. The comparison of the four studies shows that there has been a great overall improvement in oral health over this 30-year period.