The allergenic activities of egg white components were tested by radioimmunoelectrophoresis (RIEP) and RAST with highly purified proteins. Sera from 33 patients who reacted to egg ingestion were used for both methods. Ovalbumin and ovomucoid were shown to be strong allergens by both techniques. Patients varied in relative reactivity to these two allergens. Conalbumin was found to be an important allergen by RAST, but its activity was underestimated by RIEP. Lysozyme was only a weak allergen. Two sera reacted by RIEP with other neutral egg white components. Both ovalbumin and ovomucoid were found in hard- and soft-boiled egg white in immunologically recognizable form, and small amounts of conalbumin were also detectable in cooked egg. There was no significant association of pattern of reactivity with age, sex, or presence of eczema. The sera of patients who experienced gastrointestinal symptoms from ingestion of egg white were less reactive with ovomucoid than sera from patients with other symptoms.