Higher cognitive function is associated with faster choice reaction time (CRT), and both are associated with a reduced risk of mortality from all-causes and cardiovascular disease (CVD). However, comparison of the predictive capacity of CRT, an emerging risk factor, with that for established "classic" risk factors for mortality, such as smoking, hypertension or obesity, is lacking. The purpose of this study was to compare the relative impact of CRT with a range of established risk factors for all-cause and CVD mortality. The UK Health and Lifestyle Survey (HALS) is a national sample survey of adults in England, Scotland, and Wales. In 1984/85, data on lifestyle factors, socioeconomic status, and health were collected for 9003 individuals. CRT data were available for 7414 individuals. With different predictor variables having differing coding structures, we used the relative index of inequality (RII) to explore the relation of a range of risk factors with mortality by computing the risk in disadvantaged (high risk; e.g., smokers) relative to advantaged (low risk; e.g., non-smokers) persons. During an average of 20 years of follow-up, there were 1289 deaths (568 ascribed to CVD). In age- and sex-adjusted models in which all-cause mortality was the outcome of interest, CRT mean (RII = 2.57, 95% CI = 1.98, 3.33) was the second most important predictor of death after smoking (RII = 3.03, 95% CI = 2.45, 3.75). For death from CVD, CRT mean (RII = 2.31, 95% CI = 1.55, 3.43) was again the second most important risk factor for death, behind systolic blood pressure (RII = 4.37, 95% CI = 3.03, 6.29). These analyses suggest that CRT, a moderately high correlate of intelligence, is an important risk factor for death from all-causes and CVD. (Contains 2 tables.)