In order to find a relationship between normal gallbladder epithelium and dysplastic epithelium, histological and histochemical examinations were made on gallbladder specimens obtained from cholecystetomies and special attention was paid to the relationship of the different metaplasias. Epithelial pseudostratification increases in mitotic figures and hyperchromatism accord well with the degrees of dysplasia of surface epithelium. The relationship of the ratio of cell and nuclear size and complexity of glandular branching is more meaningful in degrees of dysplasia of glandular epithelium. Epithelial dysplasia in the surface and glandular epithelium was divided into three types: mild, moderate and severe. This classification was made on the basis of specimens containing dysplasia selected from an extensive gallbladder material. The frequency of dysplasias of different degrees was clarified in 71 cholecystectomia gallbladders. No dysplastic changes were demonstrated in 47 gallbladders (66.2%), and in 10 of these metaplasia was present, 24 gallbladders (33.8%) exhibited dysplastic changes; metaplasia was present in 20 cases (83.3%) and in 14 (58.3%) in the dysplastic region. Severe dysplasia was present only in one case, moderate in 6 and mild dysplasia alone in 17 cases. Dysplasia was found in glands only in 3 cases. In dysplastic epithelium, the mucin reaction was similar to that in the metaplastic epithelium. It contained mainly nonsulphated acid mucin and neutral mucin. With gradually increasing degree of dysplasia the amount of mucin. With gradually increasing degree of dysplasia the amount of mucin clearly decreased. The present results indicate that dysplasia often develops in metaplastic epithelium.