BACKGROUND: Polymorphisms at amino acid positions 16 and 27 of the beta2-adrenoceptor gene are known to be functionally relevant to asthma severity. However, there has been no data concerning frequency of beta2-adrenoceptor gene polymorphisms of their role in the expression of asthmatic phenotypes in Korean nuclear families. OBJECTIVES: The aims of this study were to evaluate frequency of polymorphisms at amino acids 16 and 27 of beta2-adrenoceptor gene and to determine their role in the expression of asthmatic phenotypes such as bronchial responsiveness and total serum IgE levels in Korean nuclear families with probands of asthmatic children. SUBJECTS AND METHOD: Two hundred forty-one individuals from 71 Korean nuclear families were enrolled with probands of asthmatic children. Asthmatic phenotypes such as asthma diagnosed by physician, serum total IgE, skin responses to common aeroallergens, and bronchial responsiveness were determined using physician's interview, ELISA and methacholine bronchial provocation tests, respectively. Polymorphisms at amino acids 16 and 27 of beta2-adrenoceptor gene were determined using PCR-based methods such as allele-specific PCR and PCR-RFLP. RESULTS: Frequency of mutant forms at amino acids 16 (Arg -< Gly) and 27 (Gln -< Glu) was 49.4% and 9.8%, respectively. Linkage disequilibrium was observed between Gly16 and Glu27 alleles and between Arg16 and Gln27 alleles, but there was no Arg16-Glu27 haplotype. Haplotypes of amino acids 16 and 27 were not associated with asthma phenotypes such as asthma diagnosed by a doctor, bronchial responsiveness to methacholine, skin responses to common inhalant aller- gens, and total serum IgE levels. CONCLUSION: The polymorphisms at amino acids 16 and 27 may not play a major role in the expression of intermediate phenotypes of asthma and asthma per se.