Background and Purpose It has been suggested that the insertion ( I )/deletion ( D ) polymorphism of the angiotensin-converting enzyme (ACE) gene is an independent risk factor for coronary artery disease, but its relation to stroke has not yet been proven. We investigated an association of ACE gene polymorphism with parental history of stroke (PHS) in patients with hypertension. Methods We studied 70 hypertensive patients (ambulatory blood pressure >140/90 mm Hg; age, 59±11 years) with (n=27) or without (n=43) PHS, defined as either one or both parents having had a stroke before 60 years of age. The ACE genotype was analyzed by polymerase chain reaction. Results Casual blood pressure and mean ambulatory blood pressure levels were not significantly different between patients with and without PHS. The incidence of left ventricular hypertrophy also did not differ significantly between the two groups. However, the frequency of the D allele was significantly higher in patients with PHS (0.72) than in patients without PHS (0.52) (χ 2 =5.472, P =.019). The frequency of the DD genotype of the ACE gene was also significantly higher in patients with than in those without PHS ( DD , 63.0%; ID , 18.5%; II , 18.5% versus DD , 32.6%; ID , 39.5%; II , 27.9%; χ 2 =6.395, P =.041). Conclusions The DD genotype of the ACE gene is associated with PHS in patients with hypertension, which is independent of blood pressure levels or presence of cardiac hypertrophy.