The prevalence of asthma in Western societies has risen steadily throughout this century，and in the last 20 years，the incidence of asthma has more than doubled. In part，this increased prevalence may be due to the steady decline of infectious diseases such as tuberculosis and influenza in developed countries. Bacillus Calmette-Guerin(BCG)is a strong inducer of the Th1 type immune response. Several studies have demonstrated that BCG can inhibit airway eosinophilia，attenuate airway hyperresponsiveness，and decrease mucus hypersecretion in animal models of asthma Mucus overproduction is a characteristic feature of asthma that can result in asthma exacerbation and/or sudden death in certain patients. It has been reported that 23％ of patients discharged from the intensive care unit following treatment for asthma die of recurrent asthma within 6 years and that mucus overproduction and mucus plugging is an underappreciated cause for their death. Kuyper et al. Measured the degree of airway narrowing and the luminal content of mucus and cells in lungs from 93 cases of fatal asthma and from lung segments from nonasthmatic subjects，they found that substantial airway plugging occurred in the vast majority of asthma cases. Studies in mice indicate that immune responses at birth are often biased toward the Th2 type responses and defective in the Th1 responses，the central defense mechanism against intracellular pathogens. Some studies observed that BCG vaccination induces a potent Th1 type immune response at birth in humans as well as in mice. Our previous study demonstrated that BCG can inhibit airway inflammation and decrease mucus hypersecretion and showed that BCG vaccination in early life could inhibit the development of airway inflammation and mucus production in a murine model of asthma. Recently，Power et al. Showed that vaccination with relatively low doses of BCG induced a Th1 response，while higher doses induced a mixed Th1/Th2 response. Thus，we sought to determine if low-dose-BCG vaccination was superior to that of high-dose BCG-vaccination on the development of airway mucus production in a mouse model of asthma.