Looking for ways to support himself, Streicher appeared in dozens of short silent stag films, often referred to as "loops," during the early 1970s. He eventually went on to appear in approximately 140 feature-length sexploitation and hardcore films between 1971 and 1989, with Deep Throat (1972) and The Devil in Miss Jones (1973) being the best known, as well as grindhouse roughies like Forced Entry (1973) and Sex Wish (1976); in the former he plays a sadistic Vietnam veteran hellbent on rape and murder - later described by Streicher as the one film he regretted appearing in - while in the latter he plays a husband-turned-vigilante seeking revenge over the rape and murder of his wife.

For the production of Deep Throat in Miami, Florida in January 1972, Streicher was hired to be part of the lighting crew, but the Director was unable to cast one of the roles and asked him to play the part. He was paid $250 for one day of acting work. Streicher was unaware that the Director had given him the name "Harry Reems" until he saw the movie.

Reems' appearance in Deep Throat led to his arrest by FBI agents in New York City in July 1974 and his indictment in Memphis, Tennessee, in June 1975 on federal charges of conspiracy to distribute obscenity across state lines. Reems called it forum shopping. He was convicted in April 1976 with 11 other individuals and four corporations.

In 1975 he published a memoir, Here Comes Harry Reems, in which he details the early years of his adult film career. Reems also appeared in a couple of mainstream films, such as the sex comedy/horror film Case of the Full Moon Murders (1973), the drama Deadly Weapons (1974), horror films Demented (1980) and To All a Goodnight (1980), the comedy National Lampoon's Movie Madness (1982) and the TV movie The Cartier Affair (1984). He provided narration for the film Mae West (1982). He also appeared in several Swedish-produced porn films, including Justine & Juliette (1975), Bel Ami (1976) and Molly (1977), as well as the mainstream SS Operation Wolf Cub (1983).

His conviction was overturned on appeal in April 1977 because his activities in making the film occurred before a U.S. Supreme Court ruling on obscenity in 1973 (Miller v. California), and Reems was granted a new trial. The charges against Reems were dropped in August.

Reems was cast in the 1978 musical film Grease as Coach Calhoun (he had done legitimate theater before turning to pornography), but out of fear that his notoriety would jeopardize the film's box office in the Southern United States, he was replaced by Sid Caesar.

Reems returned to theater in the 1979 play The Office Murders and the 1981 play What the Butler Saw.

In 1982, after an 8-year hiatus from porn, Reems returned in the porn film Society Affairs.

After years of drug abuse, Reems began his recovery in 1989. He married and converted from Judaism to Christianity. "Being the low-bottom drunk that I was, I started going around to churches," said Reems. "I called myself a church gypsy." Reems credited his conversion to Reverend Mark Heiss, a former pastor with Park City Community Church in Park City, Utah.

He was interviewed in the 2005 documentary Inside Deep Throat. Reems' entrance into the adult entertainment industry, his experience filming Deep Throat and its subsequent infamy and obscenity trials, are the subject of the 2010 play The Deep Throat Sex Scandal. During the Los Angeles run of the play, Reems died in Utah; his death was noted by the production.

Reems died of pancreatic cancer on March 19, 2013, aged 65, at the Salt Lake City Veterans Administration Medical Center. He was survived by his wife, Jeanne, his sister Janet, and a brother. He had no children.