FIELD: medicine.
SUBSTANCE: invention relates to the field of medicine, epidemiological diagnostics and quantitative estimation of factors, favouring spread of infections. Questioning of population by random choice is carried out. Tested and control groups are formed, which differ by presence or absence in them of studied factor. Level of disease incidence in these groups is compared. Risk factor, causing significantly higher level of disease incidence, is pointed out. Its epidemiological significance among the other causes of disease spread is quantitatively estimated. For this purpose is determined E - number of diseased in tested group, subjected to impact of all other factors, with exception of role of studied factor: 
where A is number of people in group, subjected to impact of studied factor, B - number of people in group, which is not subjected to impact of studied factor, D - number of diseased with infection people in group where studied factor is absent. Then by formula F=C-E is determined, where F is number of people who fell ill because of the impact of studied factor; which shows difference between number of diseased in group of individuals subjected to the impact of studied factor (C), and number of diseased in group who fell ill due to impact of all other factors with exception of possible role of studied factor (E). Then index of epidemiological significance of studied factor is determined, which is used for carrying out quantitative estimation of risk factors by formula: 
where C is number of diseased subjected to impact of studied factor, D - number of diseased in group which is not subjected to studied factor.
EFFECT: increase of accuracy of estimation of epidemiological significance of quantitative estimation of risk factors.
3 tbl, 3 ex
