A study was conducted during 1966–1968 to determine the tick and blood protozoan fauna of white-tailed deer from the Welder Refuge, south Texas. The prevalence, numbers, or both of several species of AMBLYOMMA and Theileria cervi were compared with host factors such as age, sex, and general behavior, and extrinsic factors including landscape density, and soil type. Three species of ticks, Amblyomma americanum, A. inornatum , and A. maculatum , were prevalent but not numerous on deer. Adult A. americanum were not found on neonatal fawns, adult A. inornatum preferred this age host, while A. maculatum were found on deer of all ages. A. maculatum preferred to attach to the developing antlers of males each summer. Conditions for development and activity of ticks were apparently most favorable in plant communities with vegetation characterized as “dense.” The potential of these species of Amblyomma to transmit Theileria cervi , a common infection of deer on Welder, is discussed.