ABO rs495828 polymorphism has recently been associated with risk of hypertension and cough induced by angiotensin-converting enzyme (ACE) inhibitors, which could be due to low ACE plasma activity. To study whether ABO rs495828 is associated with ACE activity. The association between ABO genotype and phenotype, and differences in ACE activity between the ABO phenotype groups were also studied. SUBJECTS AND METHODS: We genotyped 168 subjects for rs495828. ACE plasma activity and ABO histo-blood group were measured in all minor allele homozygous subjects (TT) that agreed to participate in the study (n=8) and in age- and gender-matched heterozygous subjects (GT; n=8) and major allele homozygous subjects (GG; n=8). RESULTS: A non-significant trend was found in ACE activity among rs495828 genotype groups; however the polymorphism was significantly associated with ABO phenotype (p=0.007), which in turn was associated with ACE activity (p=0.029). CONCLUSION: These results provide new evidence for the ABO-ACE relationship. Although the genetic marker studied here may be involved somehow, ABO phenotype is shown to be a better predictor of ACE plasma activity.