Two, 50-60-kg yearling reindeer (Rangifer tarandus) were inoculated intraruminally with 5,000 (reindeer 1) or 50,000 (reindeer 2) oocysts of the ME-49 strain of Toxoplasma gondii. Both reindeer became ill day 4 postinoculation (p.i.). Reindeer 2 died because of acute enteritis day 9 p.i. Histologically, extensive necrosis and destruction of the intestinal mucosa were seen. Numerous T. gondii organisms were demonstrated immunohistochemically. Reindeer 1 was treated with sulfatrimethoprim for 2 days from day 9, recovered by day 16 p.i., and remained clinically normal until the last day of observation (day 707 p.i.). It developed high antibody titers to T. gondii between days 7 and 14 p.i.