The association of socioeconomic status (SES), as indexed by educational achievement, with the prevalence, prognosis, and efficacy of treatment of hypertension in the Hypertension Detection and Follow-up Program (HDFP) was reviewed. The prevalence of hypertension varied inversely with SES during the screening program initiated to identify HDFP eligibles in 14 communities in 1973-1974. There was a strong inverse gradient of 5-year all-cause mortality with SES among the hypertensive participants referred to usual care in the HDFP. The association of mortality with SES among hypertensive subjects was eliminated by the HDFP stepped-care program. A large portion of the efficacy of the HDFP was associated with in-trial blood pressure control. Inasmuch as these results are generalizable to the nation, a large fraction of hypertension-associated morbidity and mortality in the United States was related to lower SES in the 1970s, before widespread implementation of programs resulting in increased awareness, treatment, and control of hypertension.