The role of genetic factors was reviewed with respect to the pathophysiology of bronchial asthma, sarcoidosis and cough induced by angiotensin converting enzyme (ACE) inhibitor administration. The so-called 'atopy gene' in 11q13 is not linked to atopy but is associated with serum IgE levels. The beta2-adrenergic receptor gene on 5q32-33 was found to have polymorphism by Ban I and to be related to beta2-receptor function; a defect of a 2.3 kb allele is related to lowered sensitivity to beta2-agonists. This defect is also related to higher prevalence on non-atopic bronchial asthma. The occurrence of amino acid mutation (Arg16 to Gly) of beta2-receptors was lower and Gln27 to Glu mutation is extremely rare in the Japanese population compared with Caucasians. There is polymorphism of ACE genotypes among normal subjects and patients with sarcoidosis, II, ID and DD. The genotype is a significant determinant of serum ACE activity and may determine the prognosis of sarcoid patients. Genotype II has a higher incidence of coughing induced by ACE inhibitors.