Dasyuromorphian relationships were investigated using cladistic analysis for 24 species using 77 cranial and dental features. Among the 7 extinct taxa used were 6 recently described fossil species, each well represented by cranial and dental material (3 ameridelphians, 1 peramelemorphian, and 2 dasyuromorphians). Monophyly for the Dasyuromorphia and several clades widely recognized therein is supported, but in many instances, relationships among extant dasyurids departs greatly from general consensus. Where congruence with previous investigations is evident, few taxa are united by unique synapomorphies within Marsupialia. Many clades are united by combinations of locally derived features only. Bootstrap and Bremer support is weak for most clades. Thus, although supported by cladistic analysis, the status of many synapomorphies identified in the course of this study are tentative. However, for some groups, notably Dasyuridae and a dasyurid clade inclusive of all modern subfamilies, the synapomorphic nature of some derived features appears to be robust, even where they also are present in some outgroup taxa. This argument applies to shared apomorphies of the basicranium in particular. No potential sister taxon to Dasyuromorphia is favored. The case for australidelphian and microbiotheriid affinity of some American and Antarctic fossil taxa was considered to be highly equivocal.