In order to identify the etiologic factors in childhood chronic urticaria, we studied 226 children, 122 boys and 104 girls, aged 1 to 14 (mean = 8.14) years with chronic urticaria and/or angioedema. The initial evaluation consisted of a thorough history, physical examination, and basic laboratory tests. Specific in vivo and in vitro tests were done according to the findings of the initial evaluation. Urticaria alone was present in 78.4% of the patients, angioedema alone in 6.6%, and both urticaria and angioedema in 15% of the patients. Chronic urticaria was attributed to physical factors in 6.2% of the patients, infections in 4.4%, aeroallergens in 2.2%, foods in 4%, food additives in 2.6%, and drugs in 1.8% of the patients. Overall, causal factors of chronic urticaria were found in 21.2% of the patients.