A semidocumentary is a form of book, film, or television program presenting a fictional story that incorporates many factual details or actual events, or which is presented in a manner similar to a documentary.
Stylistically, it has certain similarities to Italian Neorealism, such as the use of location shooting and employing non-actors in secondary roles. However, the viewer is not intended to mistake a semidocumentary for a real documentary; the fictional elements are too prominent.
One of the first films of this kind was Henry Hathaway's The House on 92nd Street (1945).
In the late 1940s, semidocumentary films were often associated with film noir thrillers, sharing a commitment to on-location shooting, gritty realism, and understated performances.
In the 1960s and 1970s, the semidocumentary style declined in feature films. The standard documentary had blurred the difference between itself and fiction so much that there was viewer confusion regarding what they were seeing.
Part semi-documentary, part social problem film, part film noir, Phil Karlson's The Phenix City Story (1955) is a one-of-a-kind window into a sordid and fascinating period in American crime history.