High mortality often occurs when many mule deer fawns (Odocoileus hemionus) are hand-raised together. Thymic atrophy frequently was observed in those that died. No specific pathologic agents could be identified. It was thought that there may be an adrenal corticoid-induced immunosuppression due to the stress of hand-rearing many fawns together. To study this problem, fawns were taken from the doe at two days of age and divided into four groups of five each. Two groups were from tame does and two from recently trapped wild does. Twins were separated into a single feeder group and into a multiple feeder group. There were no differences in stress between the groups as determined by urinary Cortisol and corticosterone/creatinine ratios. Humoral immunity following Clostridium toxoid vaccination was determined by immunodiffusion. Cell-mediated immunity was determined by dinitro-chlorobenzene skin tests. Serum protein electrophoresis, WBC counts, and weight gain were monitored. All groups showed similar weight gains, and humoral and cell-mediated immune responses. Serum gamma globulins, and total serum proteins were higher and segmented neutrophils lower in the fawns from the wild does throughout the duration of the eight-week study. This would indicate that these fawns had a greater passive immunity as a result of the ingestion of more colostrum, which most likely occurred as a result of better maternal care by the wild does.