BACKGROUND Previous studies have shown that psychological well being is associated with reduced risk of cardiovascular disease. However, whether well being might be specifically associated with reduced risk of hypertension has not been rigorously investigated in prospective studies. OBJECTIVE This study examined the prospective association between two measures of psychological well being and incident hypertension. METHODS Participants were 6384 healthy British civil servants aged 39-63 from the Whitehall II cohort. Psychological well being (emotional vitality and optimism) and cardiovascular risk factors (demographic characteristics, health status, health behaviors, psychological ill being) were assessed during the 1991-1994 baseline. Incident hypertension was defined by clinical measures of SBP or DBP at least 140/90  mmHg, self-reported physician-diagnosed hypertension, or treatment for hypertension. Follow-up assessments of hypertension took place approximately every 3 years through 2002-2004. Cox proportional hazards regression models estimated hazard ratios. RESULTS There were 2304 cases of incident hypertension during the follow-up period. High versus low emotional vitality was associated with a significantly reduced risk of hypertension in an age-adjusted model (hazard ratio = 0.89; 95% confidence interval 0.80-0.98). This association was maintained after controlling for demographic characteristics and health status, but was slightly attenuated after adjusting for health behaviors and ill being. Optimism was not significantly associated with hypertension. CONCLUSIONS High emotional vitality was associated with reduced hypertension risk; favorable health behaviors explained only part of the relationship. Associations did not differ by age, were similar for men and women, and were maintained after accounting for ill being.