Among 20,333 individuals aged 15 years and above, examined in urban, suburban and rural regions in the middle of Sweden, leukoedema was found in 48.9%. The sex difference, males 61.9% and females 35.9%, was highly significant (P less than 0.001). The condition was most prevalent in the age groups 25-34 and 15-24 years being 60.6 an 53.7%, respectively. Leukoedema was significantly more prevalent among individuals with some daily tobacco habit (60.0%) than among those without (36.3%) (P less than 0.001), being most prevalent among smokers. The lesion seemed to be related to the amount of smoking since it was most prevalent among heavy smokers and also the most clearly established lesions were found in this group.