Abstract—The appearance of cough in association with angiotensin-converting enzyme (ACE) inhibitors is thought to be related to bradykinin, and it has been speculated that the elicitation of adverse effects is genetically predetermined. Several polymorphisms of the human bradykinin B2receptor gene may be involved in ACE inhibitor–related cough. To investigate this possibility, we identified the −58 thymine (T)/cytosine (C) polymorphism in subjects with ACE inhibitor–related cough. We classified the study population into 4 groups: subjects with and without cough that were treated with ACE inhibitors (n=30/30), nontreated essential hypertensive subjects (n=100), and normotensive subjects (n=100). The −58T/C was genotyped by the polymerase chain reaction single-strand conformation polymorphism method. The frequencies of the CC genotype and C allele of −58T/C were significantly higher in the nontreated hypertensive subjects than in the normotensive subjects. Conversely, the frequencies of the TT genotype and T allele were significantly higher in the subjects with cough than in the subjects without cough. These tendencies were more pronounced in females. Among the promoter assays of the human bradykinin B2receptor, −58T was found to have a higher transcription rate than that of −58C. This finding seems to suggest that the transcriptional activity of promoter might be involved in the appearance of ACE inhibitor–related cough. A genetic variant of the bradykinin receptor is involved in the elicitation of ACE inhibitor–related cough. It may be possible to predict the side effects of ACE inhibitors in advance.