In 1986, the first nationwide epidemiological survey of adult oral health and attitudes to oral health care was carried out in The Netherlands. One of the aims of this study was to evaluate the prevalence and the quality (in terms of need for replacement) of amalgam and composite restorations in the Dutch adult population. A group of 600 dentate individuals, 20-44 years of age, was examined. Stratified cluster sampling included as factors age, gender, socio-economic status, and area of residence. Two additional parameters were studied: frequency of visiting a dentist and type of health insurance. Oral examinations consisted of direct (mirror and explorer) and indirect (color slides and bite-wing radiographs) observations with use of well-defined criteria. On average, 13.4 restorations per individual were present, of which 23.3% were classified as unsatisfactory. A great difference in prevalence and quality data was found among several types of restorations. Test results (ANOVA) for effects of age, gender, socio-economic status, area of residence, frequency of visiting a dentist, and insurance on the prevalence of (un)satisfactory restorations resulted nearly always in significant effects of only age and frequency of visits to a dentist. There was a tendency (p less than 0.05) for the prevalence of (un)satisfactory restorations to be higher with increasing age.(ABSTRACT TRUNCATED AT 250 WORDS)