Viet Nam had the highest reported male smoking prevalence rate (72.8-74.3%) in the world in the 1990s. Productionof tobacco products was about 0.44 kg or 600 cigarettes per capita per year in 1994 for domestic use. Populationattributablerisk per cent of lung cancer due to smoking was about 69.7%. Males in the south have a lower reportedsmoking prevalence rate (OR = 0.7) and a significant lower incidence rate of lung cancer, age-standardized-incidencerateper 100,000 (ASR): 33.1 vs 24.6 when compared to males in the north. Incidence rates of lung cancer significantlydeclined in Hanoi (ASR 34.9 –33.1 and 6.3 – 5.8) and Ho Chi Minh City (ASR 24.6 – 23.7 and 6.8 – 5.6) between 1991-1997 and at the national level between 1990-2000 (ASR 30.4 – 30.1 and 6.7 – 6.6) in males and females, respectively.This decline in incidence rate of lung cancer resulted from the great achievements of the National Tobacco ControlProgram over about a 10-year period from 1989 to help people stop smoking. The present finding should stimulatefurther primary cancer prevention efforts in developing countries, including Viet Nam. It also suggests that themethod applied to translate scientific evidence of smoking harm to people and into health policy, is a useful tool todrive people’s attitude to stop smoking and remove its human carcinogens from our society.