Background: Hostility is associated with increased cardiovascular disease mortality and morbidity and may be related to subclinical atherosclerosis; less is known about this association among women and minority groups. Methods: We examined the association between hostility and intimal-medial thickening (IMT) as well as presence/absence of plaque in the carotid arteries in middle-aged white and African American women. Hostility was measured by a 13-item questionnaire and IMT and plaque were assessed by B-mode ultrasonography in 589 participants from the Chicago and Pittsburgh sites of the SWAN. Results: In age- and site-adjusted models, each 1-point increment in hostility score predicted a significant 0.0057-mm higher mean IMT (P < .0001) and 0.0081-mm higher maximum IMT (P < .0001)-effects that were identical in magnitude to each 1-year increment in age. Adjustments for race, education, body mass index, resting systolic blood pressure, and smoking diminished these associations, but they remained significant (P ≤ .01). With hostility scores modeled in approximate tertiles, high scorers (≥6) had greater mean (P = .0005) and maximum (P = .0004) IMT than low scorers (0 or 1); moderate and low scorers did not differ (age-adjusted mean values for low, moderate, and high scorers were 0.657, 0.662, and 0.694 mm, respectively, for mean IMT; those for low, moderate, and high scorers were 0.855, 0.860, and 0.906 mm, respectively, for maximum IMT). Hostility was unrelated to presence of plaque and did not interact with race, education, smoking, and body mass index. Conclusions: Hostility is related to small but significantly greater subclinical atherosclerosis in middle-aged women; this association is not explained by traditional risk factors.