These studies sought to confirm our recent report of a patient with rheumatoid-like arthritis (RA) with clinical and immunologic milk sensitivity, to assess the prevalence of food related rheumatic symptoms, and to identify clinical and serological features of these patients. Thirty percent of our patients with RA alleged food related ("allergic") arthritis. Sixteen patients have now completed 19 double blind, controlled food challenge studies: 3 demonstrated subjective and objective rheumatic symptoms after double blind, encapsulated food challenges. The 3 were virtually asymptomatic when receiving elemental nutrition or not taking the offending foods. One was our milk sensitive patient who had increased IgG4 anti-alpha-lactalbumin, IgG-milk complexes, and delayed skin and cellular reactivity to milk; one developed inflammatory synovitis after shrimp ingestion and had increased IgG antishrimp; and another was a cardiac care unit (CCU) nurse who experienced rheumatic symptoms after exposure to nitrates. All were seronegative with palindromic symptoms and nonerosive disease. IgG, G4, A, M, and E antifood, Ig-food immune complexes, and in vitro cellular reactivity to foods were not otherwise distinctively abnormal in these or other patients with rheumatic diseases. Thus most patients alleging food induced rheumatic symptoms did not show these on blinded challenge, but some did. Probably not more than 5% of rheumatic disease patients have immunologic sensitivity to food(s). Such patients have been identified only by controlled challenge studies. These observations suggest a role for food allergy in at least some patients with rheumatic disease.