The sacroiliac joints of seven pelvic specimens were examined to determine functional, morphologic, and histopathologic aspects. The movements were measured in four intact pelvises (from two men and two women). The joint surfaces of all pelvises (from three men and four women) then were examined topographically by means of a photogrammetric method. After this, they were examined histologically to characterize any effects on function. The morphologic investigation revealed sex-specific differences. All joint surfaces from the female pelvises showed circular contours, the centers of which coincided with the iliac tuberosities. These morphologic characteristics were not discernible in the joint surfaces from the male pelvises; these had interlocking irregularities without a topographic pattern. As expected, this configuration involved distinct differences in mobility. Rotation of the sacrum was markedly less in the sacroiliac joints of men than in those of women.