Proliferative response of cord blood lymphocytes stimulated twice by food antigens and cord blood IgE concentration were measured in 131 full-term newborn infants for the prediction of allergic disorders. Through the follow-up study for 2 1/2 years, the value of stimulation index in proliferative response of cord blood lymphocytes to ovalbumin or bovine serum albumin was greater than 1.5 in 17 (sensitivity 53.1%) of 32 infants in whom allergic disorders developed and less than 1.5 in 81 (specificity 81.8%) of 99 infants who had no allergic disorders (cutoff limit of stimulation index 1.5). The sensitivity was increased (71.9%) by the combination of the cord blood IgE concentration (cutoff limit 1.0 IU/ml) and proliferative response of cord blood lymphocytes to food antigens (cutoff limit of stimulation index 1.5). The combination of the cord blood IgE concentration and proliferative response of cord blood lymphocytes to food antigens is useful for the prediction of allergic disorders. Interleukin-2 production of cord blood lymphocytes stimulated with food antigens was also measured in 24 newborn infants. Interleukin-2 activity in culture supernatants of ovalbumin- or bovine serum albumin-stimulated cord blood lymphocytes correlated well with proliferative response of cord blood lymphocytes to ovalbumin or bovine serum albumin.