In the film industry, unsimulated sex is the presentation in a film of sex scenes where the actors engage in an actual sex act, and are not just miming or simulating the actions. At one time in the United States such scenes were restricted by law and self-imposed industry standards such as the Motion Picture Production Code. Films showing explicit sexual activity were confined to privately distributed underground films, such as stag films or "porn loops". Beginning in the late 1960s, most notably with Blue Movie by Andy Warhol, mainstream movies began pushing boundaries in terms of what was presented on screen. Although the vast majority of sexual situations depicted in mainstream cinema are simulated (in early pornography, the main actors engaged in simulated sex, with inserts placed in the film), on rare occasions actors engage in real sex. The difference between these films and pornography is that, while such scenes might be considered erotic, the intent of these films is not solely pornographic.
Notable examples include two of the eight Bedside-films and the six Zodiac-films from the 1970s, all of which were produced in Denmark and had many pornographic sex scenes, but were nevertheless considered mainstream films (they all had mainstream casts and crews, and premiered in mainstream cinemas). The last of these films, Agent 69 Jensen i Skyttens tegn, was made in 1978. From the end of the 1970s until the late 1990s it was rare to see hardcore scenes in mainstream cinema, but this changed with the success of Lars von Trier's The Idiots (1998), which heralded a wave of art-house films with explicit content, such as Romance (1999), Baise-moi (2000), Intimacy (2001), Vincent Gallo's The Brown Bunny (2003), and Michael Winterbottom's 9 Songs (2004). Some simulated sex scenes are sufficiently realistic that critics mistakenly believe that they are real, such as the cunnilingus scene in the 2006 film Red Road.