Relationship of the proportion of lymphocytes in bronchoalveolar lavage (BAL) fiutd to IgE-mediated reactions and to ventilatory function was studied in two age-matched asthma groups : group A of 11 subjects with BAL lymphocytes over 30% and group B of 11 subjects with BAL leyphocytes less than 10%. Of the eleven subjects in group A, 3 (27.3%) were atopic and 4 (36.4%) were non-atopic. The proportion of BAL lymphocytes in subjects with serum IgE level more than 300 IU/ml, who were all older than 50 years, was significantly higher than that in subjects with serum IgE less than 100 IU/ml in group A (p<0.05). While of the eleven subjects of group B, 5 (45.5%) were atopic and 4 (36.4%) were non-atopic. The value of % V(25) was significantly higher in the atopics compared with the non-atopics in group A (p<0.05), although no significant difference was found in the value of % V(25) between the two asthma types in group B. The results show that an increased number of lymphocytes in BAL fluid may be enhanced by IgE-mediated allergic reactions in the elderly, and that the decreased value of % V(25) may be associated withan increased number of lymphocytes in BAL fluid in non-atopics.