Recently, the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines revised the recommendations for diagnosis of chronic hypertension. The new classification system includes a diagnosis of stage 1 hypertension in adults with blood pressures 130 to 139/80 to 89 mm Hg. We sought to compare outcomes among women at high risk for preeclampsia with stage 1 hypertension and assessed whether women with stage 1 hypertension had benefit from aspirin treatment compared with high-risk normotensive women. We performed a secondary analysis of the high-risk aspirin trial and included women with prior preeclampsia or diabetes mellitus. Among these women, 827 (81%) were classified as normotensive, whereas 193 (19%) were classified as stage 1 hypertensive. Among women receiving placebo, preeclampsia occurred significantly more often in women with stage 1 hypertension compared with normotensive high-risk women after adjustment for maternal age and body mass index (39.1% versus 15.1%; risk ratio, 2.49; 95% confidence interval, 1.74–3.55). Further, women with stage 1 hypertension had a significant risk reduction related to aspirin prophylaxis (risk ratio, 0.61; 95% confidence interval, 0.39–0.94) that was not seen in normotensive high-risk women (risk ratio, 0.97; 95% confidence interval, 0.70–1.34). Application of the American College of Cardiology/American Heart Association guidelines in a high-risk population demonstrates that in the setting of other risk factors, the presence of stage 1 hypertension is associated with a significantly increased risk of preeclampsia when compared with high-risk normotensive women. These findings emphasize the importance of recognition of stage 1 hypertension as an additive risk factor in women at high risk for preeclampsia and the benefit of aspirin.