Secondhand smoke is a major cause of disease, including lung cancer and coronary heart disease in adults and lower respiratory illness, middle ear disease, and asthma in children. Because the prevalence of smoking is much higher in men than in women, secondhand smoke disproportionately harms women. The scope of harm to women caused by secondhand smoke is both illustrated and widened by this study by Leung and coworkers. The investigators studied never-smoking married women in China, a country where 60% of men smoke compared with only 4% of women. They found that women who were exposed to secondhand smoke in the home were significantly more likely to develop tuberculosis (TB) than women who were not exposed.