Presented in the article is a mathematical urbanization model which makes one suggest that the highest probability of bloody upheavals that may ensue in the course of internal political life, should be inherent in the indices of the proportion of the urban population between 7,5 and 22,5 per cent. This hypothesis has been corroborated by an empirical cross-national test. It has been demonstrated that at early stages of modernization, the urbanization growth is accompanied by growth of the probability of particularly bloody sociopolitical upheavals; however, further growth of urbanization is accompanied by a decrease of this probability. On the whole, with urbanization higher than 15 to 22,5 per cent, statistically significant negative correlation between urbanization level and probable frequency of occurrence of bloody political upheavals is observed.