We investigated familial aggregation of pulmonary function among asthma index families and randomly selected nuclear families in a rural community in China. Measurements of pulmonary function and related risk factors were obtained from each family member. A generalized estimation equation model was used to explore the independent relation of pulmonary function among family members, with adjustment for sex, age, height, weight, education, smoking, and asthma status. There was a significant parent-child and sib-sib correlation of pulmonary function. The parent-child correlation of pulmonary function was similar for the first and second children. The correlation was greatest between sib-sibs, followed by mother-child, and less pronounced between father-child among asthma families. The rate of reduced pulmonary function in a subsequent sibling was lowest (4.0%) when both of the parents and the first sibling were in the high-pulmonary-function tertile (high-high group) and was highest (18.4%) when both the parents and the first sibling were in the low-pulmonary-function tertile (low-low group). The rates were intermediate if only the parents (7.0%, low-high group) or only the first sibling (11.5%, high-low group) was in the reduced-pulmonary-function tertile. Our data indicate a strong familial aggregation of pulmonary function in both asthma and random families in this population.