1. Using a nested case-control study of 661 non-institutionalized elderly (> or = 60 years) residents of Dubbo, New South Wales, Australia, the aim of this study is to determine whether the A1166C polymorphism of the angiotensin II type I (AT1) receptor gene is associated with hypertension in the elderly. 2. Individuals were classified as isolated systolic hypertension (ISH, n = 146), systolic diastolic hypertension (SDH, n = 188), or normotensive, age- and sex-matched controls (n = 327). AA, CC and AC genotypes were determined using restriction fragment length polymorphism analysis of DNA generated by nested polymerase chain reaction. 3. A univariate analysis (chi 2) was complemented by a logistic regression analysis, facilitating adjustment for potential confounders. The unadjusted genotype and allele frequencies in ISH or SDH subjects did not differ significantly from the control subjects (chi 2 = 3.0, P = 0.55, 4 d.f.; chi 2 = 3.0, P = 0.23, 2 d.f., respectively). After adjustment for potential confounders neither genotype nor allele predicted ISH or SDH in this cohort. 4. From this study we conclude that the A1166C polymorphism of the AT1 receptor gene is not a marker for ISH nor for SDH in this large, elderly community sample.