We hypothesize phyletic relationships among taxa of the didelphid marsupial genus Philander, based on sequences of the mitochondrial cytochrome b gene. Data are available for six taxa recognized at either the specific or subspecific levels; P. opossum opossum Lin-neaus (eastern and northeastern Amazonia), P. opossum canus Osgood (western Amazonia), P, opossum fuscogriseus J. A. Allen (southeastern Central America), P. opossum frenata Olfers (southeastern Brazil), P, andersoni andersoni Osgood (northwestern Amazonia), and P. andersoni mcilhennyi Gardner and Patton (west-central Amazonia). Haplotype divergence is minimal to non-existent (P, o, frenata) is highly divergent from all others, averaging nearly 14% in sequence divergence. Maximal divergence among haplotypes representative of the other taxa examined is P. opossum and P. andersoni. We recognize the Brazilian coastal P. frenata, as well as both P, andersoni and P. mcilhennyi, as valid species in addition to P. opossum. It is possible P. opossum is a composite, and that further studies will accord species status to the Middle American, western Amazonian, and eastern Amazonian-Guianan gray four-eyed opossums.