Airway responsiveness and lung function, endpoints with a strong genetic basis, are central to the obstructive airway diseases (asthma and COPD). In contrast, the dissection of the underlying genes requires unique sample resources, accurate and comprehensive phenotyping, and an efficient study design. To address to this three-pronged challenge, a genomic screen brought together a large, homogenous, mostly untreated sample from Anhui, China, a wealth of expertise in asthma phenotypes, and a potent study design based on extreme discordant sib pairs.