Family concordance of IgE was determined in 344 nuclear families that were studied in a community population of white families in the Tucson area. Total circulating IgE, after controlling for age, sex, smoking status, and skin test reactivity demonstrated a significant family concordance with the use of multifactional analysis of variance. This relationship was strongest among siblings, was significant as well between parents and children, and was not present between spouses. Skin test reactivity demonstrated independent family concordance with the same statistical methods. Reported diagnoses of asthma, wheeze, and allergic-rhinitis histories demonstrated a strong concordance of prevalence rates in families as well.