Life table methodology was used to estimate the probability of developing lung cancer by smoking status. Lifetime risks of developing lung cancer were estimated for six hypothetical cohorts (males, females, male current smokers, male never smokers, female current smokers, and female never smokers). Estimates of smoking mortality and incidence rates were calculated based on Canadian rates observed over the period 1987 to 1989. It was found that 172/1,000 of male current smokers will eventually develop lung cancer; the similar probability among female current smokers was 116/1,000. For those who never smoked on a regular basis the lifetime risk was substantially reduced. Only 13/1,000 males and 14/1,000 females in this category will develop lung cancer. When smoking status is not adjusted for, the lifetime risk of developing lung cancer is approximately 96/1,000 and 43/1,000 for males and females respectively.