Age is an important risk factor for mortality and unfavorable outcome after successfully resuscitated cardiac arrest. Other risk factors may interact with this relationship. We conducted the current study to quantify the influence of age on mortality and unfavorable neurologic outcome of patients surviving out-of-hospital cardiac arrest, and to determine the role of other confounding variables. This study was based on a cardiac arrest registry comprising all patients with witnessed out-of-hospital cardiac arrest of cardiac origin after successful resuscitation admitted to a department of emergency medicine between September 1991 and December 2004. We assessed the association between age and mortality and the degree of neurologic impairment, adjusting for multiple risk factors. We tested for interaction between age and all other risk factors with outcome. With each year of age the adjusted odds ratio for in-hospital death increased by 1.05 (95% confidence interval [CI], 1.04-1.07), and the adjusted odds ratio for an unfavorable neurologic outcome increased by 1.04 (95% CI, 1.03-1.06). Interaction between age and sex was present, and the analysis was stratified to sex. For men we found a steep risk increase for death and unfavorable outcome after being resuscitated from cardiac arrest, with the highest risk in the oldest age quartile. For women we observed only a slight risk increase for death and almost no risk increase for unfavorable outcome. Age is a strong independent risk factor for mortality and neurologic impairment after successfully resuscitated cardiac arrest. The risk increase with advancing age is much greater in men than in women. Therefore, in women, the influence of age on prognosis after cardiac arrest may not be very important, while in men it still plays an important role. This should be considered especially when treating successfully resuscitated women and discussing the prognosis with the medical team or the patient's family.