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Wildlife managers need to be able to assess density, distribution, and status of wildlife populations with reliable techniques. We used distance sampling from 971 point transects to estimate density and examine herd composition of desert mule deer (Odocoileus hemionus) on the Buenos Aires National Wildlife Refuge in southeastern Arizona during 4 seasons in 1996. We first conducted a pilot study to refine survey design and train observers. We also evaluated our ability to meet 4 major assumptions of distance sampling (random placement of points, objects on points always detected, objects detected at initial location, distances measured accurately). Densities varied from 0.9 (SE=0.3) deer/km(2) in summer to 2.5 (1.3) in winter. Herd size varied from 1.5 (0.1) deer/group in summer to 9.7 (.2.0) in winter. Density of females was greater than males (0.9 [0.3] and 0.03 [0.04], respectively) for all seasons combined. We found that placement of points, detecting deer at points, and not forcing deer to move from their initial location were interrelated and a function of mule deer behavior and how we approached points. Our ability to measure distances accurately was improved greatly by using distance test courses and calibration points throughout the refuge. Important considerations in using distance sampling include: 1) careful evaluation of study design; 2) establishment of permanent survey points to be used throughout time, which aids in field operations and analysis; 3) development and use of a distance test course and calibration points to train observers, practice measuring distances, and calibrate equipment; 4) development of standardized protocol to maintain consistent data collection among observers and over time; and 5) incorporation of a thorough understanding of the target species’ behavior and ecology into the survey design.