During January 1986 - September 1988 I studied the behavioral and demographic responses of mule deer (Odocoileus hemionus) to military activity on the Pinon Canyon Maneuver Site in southeastern Colorado. Military training was initiated on the site during August 1985 and recurred approximately 3 times yearly for periods of a month. During a maneuver, 3/7 of the site was used for training in accordance with a rotational land use schedule. I radio-collared fifty adult deer and 49 fawns. Female seasonal home ranges were larger in maneuver than non maneuver areas. During the nonsummer period female home ranges were larger in previous-maneuver than non maneuver areas. Fawn summer home ranges were larger in maneuver than previous-maneuver areas. Male home range sizes differed only for 50% harmonic mean transformation annual home ranges; bucks in maneuver areas had larger home ranges than in non maneuver areas. Female deer in maneuver areas exhibited significant home area shifts between pre maneuver and maneuver periods more frequently (40%) than did deer in non maneuver (control) areas (12.5%). Mule deer in military training areas may have responded to human harassment, alteration of security cover, or destruction of the forage base. I suggest that deer may exhibit a more negative response to unpredictable than predictable disturbances. Demographic data were compared to previous baseline data (1983-1984). Buck annual survival rates did not differ during 1983-1988; doe annual survival rates also were similar during this period. Summer fawn survival differed only between 1984 and 1987, being higher in 1987. All fawn mortalities either were caused or scavenged by coyotes (Canis latrans). Pregnancy rates and fawn production ranged from 88-96% and 1.4-1.7 fawns/doe, respectively. Also, fawn:doe ratios were similar during 1983-1988. Although population estimates increased between 1984 and early 1988, the population declined during late 1888. Two important confounding factors existed on the site during 1983-1988 which make it difficult to assess the effect of military activity on mule deer demographics. First, extensive cattle grazing occurred prior to acquisition of the site and continued through most of the baseline study. Secondly, coyote control was conducted during 1987-1988. These factors may have allowed the deer population to perform better under disturbance conditions. Aerial quadrat sampling was preferred over line transect sampling for censusing mule deer in low density pinyon-juniper (Pinus edulis-Juniperus monosperma) habitat. Management recommendations included training restrictions during fawning season and in severe winters, as well as revegetating disturbed areas.