In the beginning of the twentieth century the amount of extremist performances in Russia increased considerably. Representatives of several political parties which appeared in that period, adhered to radical judgments and methods in a race for power. In conjunction with this fact, government agencies of the Russian Empire had to take a series of measures of fight against extremism: to perfect the legislation, implement agents in underground organizations and conduct non-public investigations against its members. In different regions the activity was performed by the political police authorities, gendarmerie. All the questions connected with the realization of measures against extremism were coordinated by provincial gendarme departments. Operational actions were held personally by the members of local security departments with the aid of secret agents. The stuff of gendarme police departments of railways that had their own intelligence network also took part in the investigation of political crimes. The article analyses the work of the Tomsk province gendarmerie to prevent the extremist activities of the Social-Democratic organizations which in the XX century had a pronounced extremist character. The article also analyses the forms and methods of struggle against political extremism. There are examples of successful operations of the gendarmerie against the Social Democrats on the territory of the Barnaul district of the Tomsk province. The author considers the reasons of inefficiency of counterrevolutionary measures which were taken by the police of the Russian Empire and eventually led to the fall of the autocracy.