Background: The reports from in vitro studies that β₂-adre-nergic receptor (B2AR) polymorphisms are associated with agonist-promoted downregulation have evoked considerable research interest for the roles of these polymorphisms to the pathogenesis of asthma. Objective: We sought to evaluate the association between asthma phenotypes and B2AR polymorphisms at 2 sites (Arg16 → Gly16 and Gln27 → Glu27) in the general population. Methods: Four hundred forty unrelated Korean adults were randomly selected, and asthma phenotypes were determined with a questionnaire, immunoassay, skin prick testing, and methacholine bronchial provocation testing. Genotypes of B2AR polymorphisms were determined with PCR-based methods. Results: No significant association was found between B2AR alleles and haplotypes and total IgE levels, skin test responses to aeroallergens, and bronchial responsiveness to methacholine. Among the atopic subjects, however, numbers of both Arg16 alleles and Arg16-Gln27 haplotypes were negatively associated with nocturnal cough, and in contrast, Gly16-Gln27 was positively associated with it. Conclusion: B2AR polymorphisms may play an important role in the expression of nocturnal cough in atopic subjects but not in the expression of atopy and bronchial hyperresponsiveness in a general population. (J Allergy Clin Immunol 2002;109:630-5.)