Rumenitis was observed with increased frequency in a herd of white-tailed deer (Odocoileus virginianus) maintained on a high carbohydrate supplemental ration. Healing rumen scars were found in 4.4% (n=225) of animals examined in 1973; 24.1% (n=278) in 1974; and 42.5% (n=308) in 1975. The lesions often involved nearly the entire ventral blind sac of the rumen. Histopathologic studies did not define the etiologic agent and invasion by either fungi or Fusiformis necrophorus was not a prominent feature in the cases examined. Recovery appeared to be complete and the disease was not considered to be an important herd mortality factor.