BACKGROUND: Asthma is a chronic allergic disease characterized by the infiltration of eosinophils into the airway and lung. Bacille Calmette-Guerin (BCG) has been reported to be beneficial to inhibit allergic inflammation in an animal asthma model. OBJECTIVE: The aims of the study were to investigate the efficacy of BCG according to the time point of administration on asthma in a murine model. METHOD: BALB/c mice were treated with BCG (1x106 CFUs) before sensitization (-5 days) or after sensitization (+12 days) in asthma-induced BALB/c mice by ovalbumin (OVA) sensitization. Bronchial hyperresponsiveness (BHR), influx of inflammatory cells in bronchoalveolar lavage (BAL) fluid, histopathological changes in the lung and systemic immune responses were assessed. RESULT: The administration of BCG before and after sensitization suppressed asthmatic responses, including BHR, OVA-specific immunoglobulin E (IgE) production, percentage of eosinophils in BALF and pulmonary eosinophilic inflammation in the murine model compared to the control group. However, total IgE, total cell count and OVA-IgG1 were significantly suppressed by BCG before sensitization only. CONCLUSION: BCG vaccinations, regardless of administration time point, suppressed asthmatic responses in mice. The mechanism of effect of BCG before sensitization is thought to be balance Th1/Th2 immune responses, but, that of BCG after sensitization may be different from BCG before sensitization.