Trends of mortality from lung cancer in 1953-1989, age-specific lung cancer death rates of five-year birth cohorts, and the cigarette consumption were compared in Finland and the Czech Republic. While the lung cancer mortality and the smoking habits were fairly similar in Finland and the Czech Republic in the 1950s and early 1960s, contrasting differences gradually developed over the subsequent three decades in favor of Finland. In the year 1989, the Czech lung cancer death rates were much higher than the Finnish rates: in males 75.8 vs. 48.1 per 100,000; in females 9.3 vs. 6.6 per 100,000 (adjusted to the world standard population). Results obtained by descriptive epidemiologic methods support the opinion that a major part of the positive changes in the lung cancer epidemic in Finland can be explained as a consequence of the comprehensive smoking control program introduced in this country, including a significant decline in tar yield of cigarettes. In view of a long latency period between exposure and the development of disease, a continuing upward trend in lung cancer mortality is to be expected in the Czech Republic, particularly in females, resulting in an increase in the gap between Czech and Finnish lung cancer mortality. To achieve in future a falling trend in lung cancer rates even in the Czech Republic, amendments in the smoking control system according to the recommendations of the World Health Organization and International Union against Cancer are of importance.