The relation of red blood cell sodium-stimulated lithium countertransport to blood pressure (BP) and prevalence of hypertension was assessed in univariate and multivariate analyses for 2,748 men and women aged 25–74 years who participated in the baseline examination of the Gubbio Population Study in north central Italy. Since age-specific countertransport values were consistently higher for men than women, all analyses were done for men and women separately. In simple correlation analyses, countertransport was significantly related to systolic and diastolk BP in both sexes (r values 0.107–0.163). In age-adjusted analyses, countertransport was significantly related to BP level of both men and women not receiving antihypertensive treatment; mean levels were high for hypertensive persons receiving antihypertensive therapy compared with normotensive persons. Age-adjusted prevalence rates of hypertension were progressively higher for both sexes in successively higher quintiles of countertransport, almost twice as high for those in the highest quintile compared with those in the lowest quintile. Correspondingly, age-adjusted logistic regression analyses showed countertransport to be related significantly to prevalence of hypertension for both men and women (p< 0.001). Since age, body mass index, plasma total cholesterol, uric acid, glucose, urinary sodium/potassium excretion, pulse, and (for men) daily alcohol intake also were significantly correlated with BP, and in some instances with countertransport, relation of countertransport to BP was also assessed in multivariate analyses with control for these variables. For men and women, multiple logistic coefficients for the relation of countertransport to prevalence of hypertension were significant (p< 0.05) or borderline significant (0.05<p< 0.10); a person with a high countertransport value was 1.3–1.9 times more likely to be hypertensive than a person with a low value. These findings indicate that the cross-sectional relation between countertransport and hypertension generally remains significant with control for other traits known to be related to hypertension. However, prospective data are lacking as to whether countertransport is an independent risk factor for incidence of hypertension. Such data are needed for further clarification of the relation of high countertransport to the etiology of hypertension.