Cranial sizes of American mink selected for tame and aggressive behavior (towards humans) and control mink, which were not selected for behavior, were compared. Absolute sizes of the skull were demonstrated to change depending on the direction of selection. Sexual dimorphism was reduced in mink selected for aggressive behavior, because the cranial sizes of females increased and those of males decreased. Cranial traits were analyzed by the method of principal components. The groups studied differed from one another with respect to the first four components. Although the vector of selection determined the differences between the groups, some morphological changes were similar in the groups selected for tame and aggressive behavior.