Disease as a limiting factor on big game populations has been long recognized but formal studies did not begin until 1963. Three diseases studied since that time are presented to demonstrate that intelligent management decisions can be derived from knowledge about the diseases. The three diseases discussed are theileriasis, bluetongue, and salmonellosis. Disease has long been recognized as a limiting factor on Texas big game herds (Van Volkenbergand Nicholson 1943, Hahn 1945, Buechner 1950 and others). Large-scale white-tailed deer (Odocoileus virginianus) die-offs have been recorded frequently (Taylor and Hahn 1947, Taylor 1947, Hahn and Taylor 1950, Hahn 1945, Teeret aI, 1965, Marburger and Thomas 1965). These earlier workers were unfortunately ill-equipped to follow-up their superficial finds and suspicions. In the early 1960's two Texas biologists, Houston Green and Richard DeArment were involved in efforts to determine the effects of disease in white-tailed deer and pronghorns (Antilocapia americana). Despite lack of veterinary training, proper facilities, and limited funds they made some progress and served as a catalyst for future activity in this area. In 1963, a formal joint project was initiated by the Texas Parks and Wildlife Department and the Department of Veterinary Pathology, Texas A&M University to study wildlife diseases. Texas' most important big game animal, the white-tailed deer, has received the bulk of the attention. However, mule deer (Odocoileus hemiones), pronghorn antelope, bighorn sheep (Ovis canadensis), and javelina (Pecari tajacu) as well as several exotic ungulates have also been studied. These studies have revelated several disease syndromes that have important management implications. We will briefly review some of these - all of which are reported in detail elsewhere.