The riot, by about 200 members of the San Francisco Police Department (SFPD), followed a protest held by ACT UP, a militant direct action group responding to the concerns of people with AIDS.

Earlier that day, members of ACT UP had marched from the Federal Building to the Castro District to protest the United States government's actions during the ongoing AIDS pandemic.

[6] Throughout the late 1980s, ACT UP led several large-scale protests and demonstrations to both draw attention to the AIDS crisis and to pressure governments to contribute more towards combatting the disease.

[6] On Friday, October 6, 1989, ACT UP activists in San Francisco organized a march through the city to protest government inaction with regards to the AIDS pandemic.

[8] Shortly after leaving the plaza of the Federal Building and beginning the march to the Castro District, many officers on foot and several on police motorcycles began to follow along with the marchers.

[8][11][14] According to historian Emily K. Hobson, the arrest of one of the march's coordinators was a police tactic that "weakened [the] marchers' ability to communicate with one another and to respond to officers' presence".

[9] Police continued to strictly enforce the sidewalk rules for the duration of the march, which lasted for 30 city blocks, with many marchers chanting, "First Amendment under attack!

"[14] About halfway through the march, organizers stopped for a brief address to the protestors, reminding them of the AIDS-related goal of the protest and to continue in spite of the police's actions.

[14] During other ACT UP marches, it had been customary for a brief gathering to be held at the intersection, with organizers giving brief speeches and protestors chanting while some police officers would direct traffic on foot.

[16] Additionally, many protestors had begun spray-painting parts of the road with body outlines as an homage to the NAMES Project AIDS Memorial Quilt,[9] which, at the time, was headquartered about two blocks away.

[8] The Reverend Jim Schexnayder, the director of HIV/AIDS services for the Roman Catholic Diocese of Oakland, was on Castro Street at the time and was ordered into a nearby building by a SFPD officer.

[18] During the sweep, protestors began to chant the helmet badge number of a police officer who had assaulted a nineteen-year-old at the rally, rendering him unconscious and in need of several stitches.

[8] The same day, San Francisco Mayor Art Agnos released a statement to the Bay Area Reporter, a local LGBT newspaper, saying that the police's actions on October 6 were "unacceptable".

[11][23] Five days after the sweep, ACT UP issued a response in which they called for the resignation of the San Francisco Chief of Police Frank Jordan, a plan for public accountability, and disciplinary actions against officers who had been involved.

[8] Captain Richard Cairns, who had been the tactical squad leader on the night of the sweep, was placed on administrative duty and later suspended from the SFPD for beating several protestors with his nightstick.

[22] Speaking about the impact of the sweep in 2019, assistant editor John Ferrannini of the Bay Area Reporter wrote that "The Castro Sweep deepened divisions between the LGBT community and the police, which had already been frayed by decades of harassment in bars, the assassination of gay Supervisor Harvey Milk by former police officer and disgruntled ex-supervisor Dan White in 1978, and the subsequent White Night riots the following year".

[26] In 2014, when asked by the Bay Area Reporter if another incident such as the sweep could occur, San Francisco Police Chief Greg Suhr stated, "I would say very, very plainly 'Not on my watch.'