To examine the increase in eosinophils and basophilic cells in the respiratory areas of infants and young children with asthma (n = 111), we analyzed the numbers of eosinophils and basophilic cells in sputum and nasal smears. The number of children with eosinophilia grades of 2+ or greater (> or = 11 cells/five fields in x1000 magnification) in sputum and nasal smears, respectively, in each age group was as follows: 33% and 21% under 1 year, 59% and 64% at 1 year, and 79-80% and 75-78% at 2-3 years. An increased infiltration of basophilic cells according to age was also observed. Infiltration of these cells began earlier than the appearance of IgE antibodies to mite in blood.