Rates of metabolism and body temperatures were measured as a function of ambient temperature in 6 species of cuscuses, including 5 species of Phalanger and 1 species of Spilocuscus from Papua New Guinea. These species had basal rates that are typical of marsupials. Basal rate of metabolism correlated with activity level, with active species having basal rates that averaged 18% greater than inactive species. Body mass and activity level accounted for 96.6% of the variation in phalangerid basal rates. The uniformity in marsupial basal rate, independent of body mass, reflects a form of reproduction that cannot exploit high basal rates. Montane species tended to have lower thermal conductances than generally found in species limited to low altitudes.