OBJECTIVE: To study the effect of erythromycin on airway inflammation in asthmatic guinea pigs. METHODS: A model of allergic asthma was developed by sensitizing guinea pigs with ovalbumin. Twenty - four hours after the induction of asthma, cells in bronchoalveolar lavage fluid (BALF) were categorized, the right lung was processed for histopathological examination and the numbers of eosinophils, neuthrophils and monocytes in the BALF and bronchial lumen were counted. Eight normal guinea pigs were used as the controls. RESULTS: The numbers of eosinophils, neuthrophils and monocytes in the BALF [(10.9 ± 1.2), (3.9 ± 0.7) and (4.2 ± 1.0) × 108/L, respectively] and bronchial lumen [(73.6 ±8. 8), (7.1 ± 1.9) and (3.5 ± 0.7) high powered field (HP), respectively] of the asthma group were significantly higher compared to those in the BALF [(0.5 ±0.1), (0.4±0.1) and (2.0 ± 0.4) × 108/L, respectively] and bronchial lumen [(5.5 ±1.6), (1.2 ± 0.9) and (0.7±0.5)/HP, respectively] of the controls ( P< 0.01 or 0.05). After pretreatment with erythromycin, eosinophils neutrophils, and monocytes in the BALF [(3.3 ± 0.5), (1.710.2) and (3.1 ±0.7) × 108/L, respectively] and bronchial lumen [(38.7 ± 5.6), (3.7±0.8) and (2.2 ±1.0)/HP, respectively] of the asthma group decreased significantly ( P <0.01 or 0.05), but remained higher than those of the controls. CONCLUSIONS: Erythromycin alleviates but does not block completely airway inflammatory reactivity.