The main neurological causes of morbidity and mortality are stroke and dementia. We contend that the most relevant and readily communicated risk estimate for stroke and dementia is lifetime risk, which is the probability of someone of a given age and sex developing a condition during their remaining lifespan. Lifetime risk estimates describe the population burden; however, they can be refined with risk-stratified models to enable individual risk prediction. Community-based data on a group of North Americans of European descent indicate that the lifetime risk of stroke for a middle-aged woman is 1 in 5 and for a middle-aged man is 1 in 6. The lifetime risk of stroke was equal to the lifetime risk of dementia and equal to or greater than the lifetime risk of Alzheimer's disease (1 in 5 and 1 in 10 for women and men, respectively), and the lifetime risk of stroke or dementia was greater than 1 in 3. Thus, the lifetime burden attributable to common neurological disease is immense.