We investigated habitat use patterns of mule deer (Odocoileus hemionus) in northeastern Oregon relative to the successional stages of the bluebunch wheatgrass (Agropyron spicatum)-Sandberg bluegrass (Poa secunda) habitat type, and other vegetative types from June 1983 to June 1985. Stands approximating the composition of the climax community, which contained highest vegetative diversity, were preferred by deer. Communities most preferred in summer were on northand east-facing slopes. Mule deer use of habitats in spring was related to early spring plant growth on steep southand west-facing slopes. J. WILDL. MANAGE. 53(2):314-319 Evaluations of habitat use patterns of mule deer have not considered rangeland succession as extensively as forest succession (Black et al. 1978, Hanley 1984). Widespread grazing of rangelands has created extensive areas in various successional stages that mule deer inhabit; e.g., the mule deer winter range on the Umatilla Indian Reservation (UIR) in northeastern Ore-