In one-way sensitivity analyses of assumptions with respect to effectiveness, adherence, costs of monitoring and medications, and side-effect frequency, all primary prevention strategies in all men and in women with stage 2 hypertension were projected to be cost-effective (Table S12 in the Supplementary Appendix). Strategies for women with stage 1 hypertension between the ages of 35 and 59 years were projected to range from $51,000 to $100,000 per QALY gained (thus falling into the intermediatevalue range) on the assumption that the diastolic blood-pressure level would be reduced by 1.6 mm Hg less, drug costs would be increased by a factor of 2.4, monitoring would be twice as frequent, or side effects would be twice as costly or 50% more severe. The treatment of women between the ages of 35 and 44 years without diabetes or chronic kidney disease was cost-effective only if an additional $150 or more could be saved per person treated each year. Treatment of women between the ages of 60 and 74 years with stage 1 hypertension was of intermediate value on the assumption that drug costs would increase by a factor of 2.4. Health gains from hypertension treatment persisted among all adults between the ages of 60 and 74 years and among men under the age of 60 years with stage 2 hypertension, even on the assumption that the inconvenience of taking antihypertensive medications would decrease the quality of life. The same pill-taking disutility led to a projected loss in QALYs in all patients with stage 1 hypertension and in women under the age of 60 years with stage 2 hypertension. Because lower adherence reduced effectiveness and costs in equal proportions, a reduction of 25% or 50% in the main assumption for adherence (effectively, adherence rates of 56% and 38%, respectively) had little effect on the results. The assumption of full intervention costs but a 1-year delay in realizing health gains attenuated incremental cost-effectiveness ratios only slightly.