Eighty-three Didelphis virginiana from the Portland metropolitan area were collected and studied from December 1974 through May 1976. Males averaged 3394 g, females 2318 g. An annual sex ratio of 68.7:31.3 was recorded. Data indicate the possibility of a year-round breeding season and suggest the occurrence of three peaks of reproductive activity: January-February, April-May and October-November. The six primary foods consumed annually are: leaf litter, mammals, gastropods, earthworms, grasses and pet food. Seasonal composition and diversity in the diet is marked. Five new parasite-host records were established. These include mites: Androlaelaps fahrenholsi, Haemogamasus nidi, Eulaelape stabularis tick, Ixodes angustus, and a nematode, Toxocara canis. Both minimum and maximum temperature, and perhaps precipitation to a lesser degree, affect the activity of the species. Nest building by an immature opossum is described.