A population sample of 2464 persons between 20 and 70 years of age was invited to participate in a screening study designed for establishing gallstone prevalence rates. The diagnosis of gallstones was based on an ultrasonographic examination. The overall response rate after the primary invitation was 55.6%. Gallbladder stones were diagnosed in 300 persons, giving a crude prevalence of 21.9%. Total age-adjusted prevalence rates were 17.7% in men and 21.2% in women. From age group 20-29 years to age group 60-69 years the prevalence rates increased from 4.9% to 37.0% in men and from 6.0% to 41.3% in women. The age- and sex-specific rates are comparable to those of more recent studies from Scandinavia but are markedly higher than prevalence rates in a Norwegian study from 1960.