Eighty-three oral food challenges were performed on 25 patients with a history of immediate adverse reaction to foods. Seventy-one food challenges were performed in 24 patients, whereas 12 placebos were administered to nine patients. Of the 71 food challenges observed, 12 were positive in 10 patients. All challenges with placebo were negative. Doses of challenge foods provoking observable reactions ranged from 5 to 100 gm. The clinical signs and symptoms noted on food challenge reproduced those reported by history. Reactions were mild, generally self-limited, and were not accompanied by elevations in urinary histamine. A plasma histamine elevation was observed in one patient. A 10- to 12-mo follow-up survey of nine patients with negative food challenges revealed that six patients had resumed eating the challenge food on a regular basis without experiencing adverse reactions, whereas three patients continued to avoid the challenge food. All 10 patients with positive food challenges continued to avoid the challenge food.