Hypertension has been reported in 8-32% of HIV-infected individuals. Large interarm blood pressure differences (IABPD) may cause misclassification of blood pressure (BP) status. The objectives of this study were to determine the magnitude and factors associated with IABPD in HIV-infected women and uninfected controls. Using automated devices, two BP recordings were measured and averaged from each arm in Brooklyn enrollees of the Women's Interagency HIV Study. Absolute IABPD was calculated for each patient. Among 335 subjects, 238 were HIV infected and 97 were uninfected. Mean systolic and diastolic IABPD were 6 +/- 5 mm Hg and 4 +/- 3 mm Hg, respectively. Twenty-six percent of subjects had systolic IABPD >10 mm Hg and 6% had systolic IABPD >20 mm Hg. Fifteen percent of subjects had diastolic IABPD >10 mm Hg. Interarm BP differences were not associated with HIV serostatus, CD4(+) cell count, and use of highly active antiretroviral therapy. Systolic IABPD >20 mm Hg was associated with obesity (ORadj 5.37, 95% CI 1.47, 19.65), and LDL cholesterol above 160 (ORadj 9.12, 95% CI 2.53, 32.88). Right arm BP measurement resulted in 10% of subjects with high/uncontrolled BP. Bilateral arm BP measurement increased the yield to 15% (p < 0.001). In conclusion, systolic and diastolic IABPD are common and appear to be of clinically important magnitude. Systolic IABPD are related to cardiovascular risk factors but not to HIV-related factors. Bilateral BP determination is important to detect and manage hypertension as well as for accurate cardiovascular risk assessment.