Causes of mass turmoils, uprisings and revolutions have often been linked to “youth bulge” effect – that is, a considerable rise in the share of youth in adult population. In case of 1905 Russian revolution issue of “youth bulge” and its role remains disputable. Using 1897 census data and current demographic statistics, author of the paper demonstrates that “youth bulge” did exist in Russia. Practical effects of a considerable increase of youth cohort are analyzed. One of them was exodus of youth in the cities and an increase of proletarian layer in population, the second being increasing numbers of students and active student movement.