There has been some debate in the scientific literature on whether or not two subspecies of the swamp rabbit, Sylvilagus aquaticus aquaticus and S. a. littoralis, exist. The latter subspecies is believed to be restricted to habitats along the coast line of Texas, Louisiana, Mississippi, and Alabama. The objectives of this research were to record a standard set of cranial measurements from voucher specimens of the swamp rabbit that are housed in natural history collections and use multivariate statistics to assess the degree of geographic variation among populations throughout Louisiana. Morphological variation was assessed by taking 26 cranial measurements with a digital caliper and rounded to the nearest 0.01 mm. We performed analysis of variance (ANOVA) to determine the extent of secondary sexual variation and a multivariate analysis of variance (MANOVA) to detect differences in morphological variation among sampling units. Our results indicated no significant secondary sexual variation between male and female rabbits. Also, no significant difference was detected between sampling units of S. a. aquaticus and S. a. littoralis. Based on these results we suggest all swamp rabbit populations be referred to as S. aquaticus with no subspecific designation.