Housing instability, a growing public health problem, may be an independent environmental risk factor for hypertension, but limited prospective data exist. We sought to determine the independent association of housing instability in early adulthood (year 5, 1990-1991) and incident hypertension over the subsequent 15 years of follow-up (years 7, 10, 15, and 20) in the Coronary Artery Risk Development in Young Adults (CARDIA) study (N = 5,115). Because causes of inadequate housing and its effects on health are thought to vary by race and sex, we hypothesized that housing instability would exert a differential effect on incident hypertension by race and sex. At year 5, all CARDIA participants were asked about housing and those free of hypertension were analyzed (N = 4,342). We defined housing instability as living in overcrowded housing, moving frequently, or living doubled up. Of the 4,342 participants, 8.5 % were living in unstable housing. Across all participants, housing instability was not associated with incident hypertension (incidence rate ratio (IRR), 1.1; 95 % CI, 0.9-1.5) after adjusting for demographics, socioeconomic status, substance use, social factors, body mass index, and study site. However, the association varied by race and sex (p value for interaction, <0.001). Unstably housed white women had a hypertension incidence rate 4.7 times (IRR, 4.7; 95 % CI, 2.4-9.2) that of stably housed white women in adjusted analysis. There was no association among white men, black women, or black men. These findings suggest that housing instability may be a more important risk factor among white women, and may act independently or as a marker for other psychosocial stressors (e.g., stress from intimate partner violence) leading to development of hypertension. Studies that examine the role of these psychosocial stressors in development of hypertension risk among unstably housed white women are needed. © 2012 The New York Academy of Medicine.