Food allergy (FA) practice varies widely. To report differences between allergists and nonallergists regarding diagnosis, treatment, and prevention of FA. A 2-page questionnaire was mailed to 3,000 allergists and 4,000 nonallergists. We previously published the findings on prevalence and manifestations. Herein, we report the findings on food allergens, diagnosis, treatment, and prevention. Responses were received from 584 (19.5%) of the allergists and 77 (1.9%) of the nonallergists. Because of the nonallergists' low response rate, descriptive comparisons were made without emphasis on statistical significance. Allergists and nonallergists differed in their rankings of the 5 most common food allergens. Nonallergists differed markedly from allergists in the diagnostic methods, using more leukocytotoxic tests (10.9% vs 0.3%), specific IgG4 tests (33.8% vs 6.0%), and intradermal tests (40.0% vs 9.5%), but fewer percutaneous skin tests (44.7% vs 98.9%), specific IgE tests (73.4% vs 97.8%), and challenges (61.1% vs 87.6%). They also differed in their use of open, single-blind, and double-blind challenge tests. Allergists were more likely to rely on elimination of proven food allergens and less likely to use conventional elimination diets, rotation diets, and sublingual or subcutaneous hyposensitization. Allergists were more likely to recommend a diet regimen during pregnancy (76.7% vs 35.3%) and lactation (91.1% vs 72.9%), breastfeeding (93.6% vs 84.3%), hydrolysate formulas (83.5% vs 64.3%), and withholding solids until the age of 6 months (89.4% vs 70.0%). Differences were noted between nonallergists and allergists regarding causes, diagnostic methods, treatment, and prevention of FA, indicating the need for more education in this area.