Out of 2392 men aged 45--59 years, examined in accordance with the WHO standard methods for detection of risk factors of ischaemic heart disease (IHD), within the follow-up period from March, 1972, till February, 1978, 96 persons died. Considerable differences were found in the proportion of ex-smokers and non-smokers in the group of individuals without IHD and among patients with IHD. Among all deceased subjects in those deceased of IHD and among the persons without IHD the proportion of smokers was considerably higher than the proportion of non-smokers. In the smokers the most frequent cause of death were malignant tumours. Overall mortality and mortality due to IHD were markedly higher in smokers as compared to ex-smokers. Considerably lower values of systolic, diastolic arterial pressures and cholesterol, lower body mass, and lesser skin-fold thickness were found in the living smokers. Blood sugar levels were not different in smokers, ex-smokers, and non-smokers. In the light of the present study, smoking is the factor most increasing the risk of death of malignant tumours and considerably increasing the probability of death of IHD.