In order to study the progression of proximal caries lesions and the quality of restorations, a sample of individuals in Gothenburg, Sweden was radiographically examined at the ages of 16, 19 and 22. By means of an index system every proximal tooth surface was given a diagnosis and differences between examinations were evaluated by a score system. Of all decayed and filled surfaces observed at the age of 22 more than 70% were already established at the age of 16. During the 16--19 year interval more than twice as many new carious lesions were developed than during the 19--22 year interval. The decrease in the number of new lesions during the last interval was accompanied by a slower progression of already existing lesions. Both factors resulted in a lower mean value with regard to scores during the 19--22 year interval compared with the preceding one. However, great individual differences were noted and 22 percent of the individuals exhibited larger score values during the last interval than during the first. Relatively seen the number of restorations with overhanging margins was lower at the final examination than at the previous ones.