In 1992 and 1999, dental health in 20- to 79-year-old adults from the canton of Zurich was assessed with a standardized method (WHO). The aim was to establish the current state and changes of dental health. Roughly half of the 852 approached adults selected by chance did take part. In 1992 and 1999, the mean number of unfilled, decayed teeth (DT) was on a low level in all age classes (0.2 to 1.8 depending on age class and examination year). The number of missing teeth (MT) in older adults (60-79) was on a high level (8.8 to 13.4). The number of filled teeth (FT) was highest (14.8 to 16.2) in middle-aged adults (40-59). Total loss of teeth was found only in older adults (60-79). Lack of a "functional" own dentition (5 teeth present in each quadrant) was found in roughly half of the 60- to 69-year-olds and two thirds of the 70- to 79-year-olds. In 1999, the state of the roots and loss of attachment was assessed. Wedge-shaped defects were found in more than half of the middle-aged adults (40-59). Carious roots were found in more than half of the 70- to 79-year-olds. Nearly half of the 70- to 79-year-old participants showed "severe" loss of attachment (> or = 6 mm). In the short period from 1992 to 1999, a significant decrease of 3.7 DMFT was found in 20- to 49-year-old adults. The decrease of 0.9 MT and 2.1 FT means also a decrease in treatment need in this age segment. In contrast, in the 50- to 79-year-olds no change in dental health could be established.