A random sample of 540 men and women aged 70 years who lived in the western part of Copenhagen County was drawn from the National Central Person Register. The response rate was 74.8% among men and 63.7% among women. Each subject had the gallbladder examined by ultrasonography. The prevalence of gallstone disease was 30.2% and 18.8% among women and men, respectively, being significantly higher among women. Prevalence was assessed in relation to different social and clinical variables. In the univariate analyses gallstone disease was significantly associated with familial occurrence of gallstone disease and high body mass index, whereas it was not significantly associated with social status, childbirths, age at menopause, usage of menopausal hormone therapy, abstinence from alcohol, history of smoking, slimming treatments, and physical activity. By means of a multivariate analysis the history of smoking was found to be significantly associated with gallstone disease when body mass index was taken into account. The significant sex difference disappeared when childbirths and age at menopause were included, which means that clinical variables specific for women in the fertile period could explain the sex difference in gallstone prevalence.