"The Interview," the Sony Pictures film about a fictional plot to assassinate North Korean leader Kim Jong Un, opened in more than 300 cinemas across the United States.
Co-directors Evan Goldberg and Seth Rogen, who also co-stars in the low-brow comedy with James Franco, surprised movie goers by appearing at the sell-out.
At the screening of the film at a cinema in Los Angeles, they briefly thanked fans for their support.
Sony Pictures this week back tracked from its original decision to cancel the release of the $44 million (€36m) film after major US cinema chains pulled out because of threats by the group claiming responsibility for a destructive cyber attack on Sony last month.
The United States blamed the attacks on North Korea.
Cinema managers and patrons alike said they believed there was nothing to fear, and the initial screenings were uneventful.
The audience at the first screening of the film in New York City, at the Cinema Village in Manhattan's Greenwich Village, remained silent during a scene showing the death of Kim Jong Un in the downing of his helicopter.
Matt Rosenzweig, 60, of Manhattan, said the moments that drew the most applause had to do with the idea of acting against censorship rather than animosity toward North Korea.
The film is available online in the US on Google Inc's Google Play and YouTube Movie and to customers of Microsoft's Xbox Video, as well as on a Sony website, www.seetheinterview.com.
It can be seen in Canada on the Sony site and Google Canada's website.
A Sony spokeswoman said she had no figures on the number of downloads so far or on how well the movie was doing at the box office.
A spokesman for Microsoft also said he had no information yet on downloads and declined to say if the company had taken any special security measures or stepped up customer support.
Cinema Village manager Lee Peterson, who declined to provide details of security precautions, said the New York Police Department planned to have officers outside the cinema.
He said he had also heard from the Federal Bureau of Investigation.
There was no visible police presence outside or inside the Cinema Village for the first screening.
In Los Angeles, where the film drew a sell-out crowd for the 12.30am showing, people who held cups of warm cider as they waited for the cinema to open said they came to show support for freedom of speech and freedom of choice.
The movie, which is playing in cinemas in major metropolitan areas as well as in smaller cities ranging from Bangor, Maine, to Jasper, Indiana, features Mr Rogen and Mr Franco as journalists who are recruited by the CIA to assassinate the North Korean leader.
Sony decided to release the film after US President Barack Obama, as well as such Hollywood luminaries as George Clooney and Republicans and Democrats in Washington, raised concerns that Hollywood was setting a precedent of self-censorship.
In Los Angeles' San Fernando Valley, where the first screening at 11.45am was only half full, some film goers were blunt about their reasons for attending.
The audience in Manhattan exited the cinema to a throng of network TV cameras and a crowd of people lined up for the next showing.
North Korea has called the film an "act of war."
Most fans simply called "The Interview" a funny movie.
Ken Jacowitz, a 54-year-old librarian from the New York borough of Queens, called it "a funny film made by funny people." He had a message for North Korea and the hackers: "You have given this movie whole new lives."
