We assessed the spatial and genetic organization of the island spotted skunk (Spilogale gracilis amphiala) on Santa Cruz Island, California. Home ranges of adults were largely non-overlapping, consistent with expectations for a solitary species. Contrary to expectations, we found no evidence of a matrilineal spatial structure. Relatedness of adult females was not negatively correlated with geographic distance, nor was it positively correlated with overlap of home ranges, possibly because of excessive dispersal caused by exceptionally high densities. We did find evidence of a patrilineal structure at one study site, where relatedness among males was negatively correlated with distance. The explanation for differences between males and females in genetic structure is uncertain, but it may reflect the differential influence of high density on dispersal of males and females.