The Control Patrols (Spanish: Patrullas de Control) of the Central Committee of Anti-fascist Militias of Catalonia was a public order force, mainly composed by CNT-FAI militias, replacing the official police forces which had been discredited after the coup d'état of July 1936, as about half of the police forces had joined the Nationalist side. In Barcelona's neighborhoods, and in many towns of Catalonia, committees were created that managed their own local militias, and even coordinated to go to the front. The number of armed people in Barcelona was quite large due to the assault on the San Andrés Barracks, after which 30,000 rifles had been seized and were scattered throughout the city.

The organization was created in August 1936 with the mission of prosecuting collaborators of the military revolt. After a violent phase followed by a progressive control of the Generalitat of Catalonia, the patrols were dissolved in June 1937 due to the military and political control taken by the Communist Party of Spain and other pro-Soviet forces. During their short period of existence, these groups detained and executed many members of the Church, Carlists, and other people accused of being fascist or pro-nationalist in Barcelona and the surrounding areas.

This revolutionary public order force acted in parallel to the Police Headquarters under the direction of the Junta de Seguridad del Comité. The patrols were coordinated by a General Secretariat, located at 617 Gran Via de les Corts Catalanes in Barcelona. The investigation services of the CNT-FAI functioned in cooperation to the control patrols. The patrols were divided into territorial sectors, in addition to port and railway patrols. Each section had a detention center and a delegate. The main detention center was found in the former convent of San Elías, at the foot of Tibidabo. Control of the sections was shared among parties with representation on the Junta de Seguridad del Comité. The CNT-FAI had control of the General Secretariat and the simple majority in most sectors.

Its scope of action was the districts of Barcelona, which at this time (August 1936) was experiencing a wave of revolution and violence. Numerous murders and crimes were taking place, with FAI releasing a document dated 30 July in which it distances itself from the excess violence:

"An Investigation Committee functions as an appendix to the Committee of Anti-Fascist Militias, which will take care of verifying all the denunciations that are made about the activities of the elements involved in the past fascist movement. This committee is the only one, apart from the Superior Police Headquarters, which, from this moment, has the right to order and carry out house searches. WHATEVER IS DONE ON THE EDGE OF IT WILL BE AN OUTRAGE. And the FAI is willing to put an end to those groups of the unconscious, outside the control of our Organization, who, who knows for what purposes, dishonor the revolutionary movement of the people, who have taken up arms against fascism. We do not know what elements these are, but we affirm with energy, whoever they are, they are denounced by their own actions, in the best of cases, as cloudy souls, in which the just instinct of the people is adulterated, awakening primitive voices nested in the darkest of his conscience." - Solidaridad Obrera and Boletín de Información.

The sectors consisted of militiamen from different political affiliations: Confederación Nacional del Trabajo (CNT), Esquerra Republicana de Catalunya (ERC), Unión General de Trabajadores (UGT) and Partido Obrero de Unificación Marxista (POUM). The distribution of militiamen per affiliation was as follows:

The CNT, despite having almost half of the militiamen of the patrols, only had delegates in 4 of the sectors (Poblenou, El Clot-El Poblet, Sant Andreu and Sants-Hostafrancs).

The Patrols were the work of the Central Committee of Anti-Fascist Militias of Catalonia, and were promoted by the CNT and the FAI, and later supported by the rest of the Popular Front organizations to put an end to the violent chaos which occurred in Barcelona. In principle, it was about putting an end to the supporters of the military uprising who often fired from the city's balconies and roofs. But gradually their purpose extended and included containing the revolutionary violence of different neighborhood committees and unions. In these first months there were militias belonging to each political organization or union.^{[citation needed]}