The reproductive biology of Dromiciops gliroides is described from five females collected during spring (October, December 1984) in southern continental Chile. Developmental morphology of intra-uterine embryos (October litters) was examined by microscopic analysis and compared with morphological attributes of 8 pouched young (December litters). Intra-uterine embryos demonstrate ontogenetic features characteristic of altricial neonates, which migrate from the urogenital opening to the marsupium in order to complete the later stages of development. D. gliroides apparently is a monoestrus, seasonal breeder producing one litter per year. Maximum recorded litter size is four, with birth occurring in early spring (October). The life cycle of D. gliroides is subdivided into seven distinct periods: pair formation, intra-uterine development, parturition, intra-marsupium development, nocturnal family excursions, and juvenile independence. Phylogenetic relationships of D. gliroides to Neotropical and Autralian marsupials are considered by comparing aspects of reproductive biology and early life history characteristics