In developed countries lung cancer mortality has been shown to be related to lifestyle, occupational and environmental aspects, diet, and other factors which may vary widely from one region to another. To investigate inter-area differences in lung cancer mortality and cigarette smoking a descriptive study has been carried out in three areas of Italy and two republics of Czechoslovakia. The highest death rates from lung cancer were found in the Czech Republic and Northern Italy, for both sexes. Analysis of age-specific rates by birth cohort, comparing all five areas, showed the greatest differences in trends between Slovakia and Northern Italy in men, and between the Czech Republic and Southern Italy in women. The lowest rates were observed in Southern Italy throughout the period under study, particularly among women. Making allowance for the latency period between the onset of exposure and the development of the disease, data on the occurrence of lung cancer could be interpreted looking at previous smoking habits. An imperfect overlap between the trend of cigarette smoking and the corresponding lung cancer mortality pattern was present in Northern and Southern Italy, a finding suggesting that even non-smoking-related factors could have played a significant role in lung cancer aetiology.