Background: RANTES (regulated on activation, normal T expressed and secreted) has been shown to possess chemotactic activity for eosinophils. Eosinophils have been considered to play a key role in the allergic inflammation through the release of inflammatory molecules such as radical oxygen products. Thus, in this study, we examined the effect of RANTES on radical oxygen products from eosinophils, Methods: Eosinophils were isolated from heparinized venous blood of patients with bronchial asthma by the modified CD16-negative depletion method. Radical oxygen products were examined in terms of lucigenin-dependent chemiluminescence, To a mixture of 50 mu l of eosinophils (2 x 10(6)/ml) and 50 mu l of lucigenin (5 x 10(-4) M), 50 mu l of calcium ionophore A23187 (final concentration 10(-5) M) was added, and radical oxygen products were determined for 600 s, Results: RANTES treatment resulted in the enhancement of peak value (0.64+/-0.23 RLU) and integrated value (119.08+/-20.52 RLU) as compared to untreated cells (0.15+/-0.03 RLU, 29.48+/-8.92 RLU, respectively), Conclusion: We could conclude that RANTES might play an important role in the pathogenesis of allergic inflammation through involvement in selective eosinophil infiltration and eosinophil activation by augmentation of eosinophil oxidative metabolism.