"CHEKA. 1917—1922. Encyclopedia" is a systematized scientific reference publication that accumulates modern knowledge of the All-Russian Extraordinary Commission for Combating Counter-Revolution, Sabotage and Crimes ex officio under the SNK of the RSFSR. It gives an interpretation of terms (concepts) that reveal the main areas of activity of the bodies and troops of the Cheka: the fight against economic crimes; suppression of subversive actions of the enemy's special services and counter-revolutionary organizations; ensuring the safety of the Red Army and Navy; participation in the suppression of the insurgency, rebellion and the fight against political banditry; liquidation of opposition parties and others. The book contains biographies of employees of the central and provincial apparatus of the Cheka, Soviet and party leaders, representatives of science and culture, whose activities were associated with the Cheka, leaders of anti-Soviet organizations, the White and rebel movement, agents of Western special services under investigation by the Cheka during the "Red Terror." And this is more than 1200 personalities.