In this study, we used the enzyme-linked immunosorbent assay (ELISA) to evaluate the changes of serum interleukin-2 (IL-2), interleukin-2 receptor (IL-2R), and suppressor/cytotoxicity factor (CD8) in house dust-sensitive asthmatic children during hyposensitization. Patients before immunotherapy presented significantly higher serum levels of IL-2 and IL-2R than normal subjects (p less than 0.001), but these levels became normal after three years of hyposensitization. No significant difference of serum CD8 level was noted between pretreated patients and normal controls. Although the serum CD8 level in treated patients also decreased after three years of immunotherapy, this decrease was not significant compared with the pretreated patients (p greater than 0.05). This study suggests that serum IL-2 and IL-2R markers might be helpful in analyzing allergic states associated with immune activation and in evaluating the therapeutic effects of hyposensitization.