Spatial patterns of sexual dimorphism in minks (Mustela vison) from 35 localities in North America were examined using 25 cranial characters to test predictions of the resource partitioning hypothesis of sexual dimorphism. Specific hypotheses evaluated were that trophic structures would be among the most dimorphic and would not be strongly correlated to body size characters. Twenty of 25 characters were significantly larger in males. Predictions of the resource partitioning hypothesis were not supported as canine diameter, a widely used indicator of resource partitioning, was not sexually dimorphic and there was a relatively large correlation between body size traits and trophic traits. Significant spatial variation in degree of dimorphism was found. The patterns of sexual dimorphism from principal components analysis indicated that largest degrees of sexual dimorphism were found in minks from Pennsylvania and Florida and least degrees of dimorphism were in minks from Alaska and Quebec. Sexual dimorphism may have an important temporal component which should be investigated in further studies.