Although he utters only four audible words in the entire first season of the show, the Smoking Man eventually develops into the series' primary antagonist.

In his early appearances, he is seen in the offices of Section Chief Scott Blevins and Assistant Director Walter Skinner, Mulder and his partner Dana Scully's supervisors.

An influential man working for the powers that be, he is a key member in a government-conspiracy unit known only as the Syndicate, who are hiding the truth of alien existence and their plan to colonize Earth.

The same episode reveals that by the early 1960s he was a United States Army Special Forces captain involved in black operations and intelligence, and that he served alongside Bill Mulder.

As part of the mission, the Smoking Man told the designated patsy, Lee Harvey Oswald, to bring the curtain rods as a way to frame him for the murder.

He did the deed himself because he had "too much respect for the man," and chose to frame a white racist because of his own sympathy for the American civil rights movement.

He was in direct talks with Saddam Hussein and involved in one way or another on the Anita Hill–Clarence Thomas controversy, moving the Rodney King trial to Simi Valley, California, keeping the United States government from interfering in the independence of Bosnia and Herzegovina, the Academy Awards nominations, keeping the Buffalo Bills from ever winning the Super Bowl, drugging the Soviet goalkeeper Vladislav Tretiak before the Miracle on Ice, and executing extraterrestrials that survived landing on American soil.

[10] In "One Son", Jeffrey finds out that his father, the Smoking Man, forced his mother Cassandra to undergo medical treatments that led to several nervous breakdowns during his childhood years.

Knowing of the colonization plan, the Alien rebels return to Earth to try to persuade the Syndicate to join their side against their war with the Colonists.

Not believing in the strength of the Alien rebels, the Syndicate members meet at El Rico Air Base to be transported to a spaceship to survive the colonization.

In the end, Alex Krycek and Marita Covarrubias betray him in the episode "Requiem", throwing him down a flight of stairs, where they presume him to be dead.

In the season finale, "My Struggle II", the Smoking Man puts into motion the conspiracy he had been working on all these years, releasing chemtrails into the atmosphere which trigger immune system breakdowns throughout the American population, which had been infected by the Spartan virus through mandatory flu vaccinations.

In the season 11 finale "My Struggle IV", the Smoking Man and Reyes follow Mulder, Scully and Skinner to an abandoned factory where they are chasing down William.

The Smoking Man confronts "Mulder" (who is actually William in disguise) by a waterfront, and during the standoff shoots him in the head and causes him to fall into the water.

The real Mulder appears and shoots the Smoking Man, who realizes that he has killed William, and he falls off the edge and into the water, with his body then carried away by the current.

Prior to the tenth televised series of The X-Files in 2016, Chris Carter worked with IDW Publishing in 2013 to produce a comic-book continuation of the show.

[17] The Smoking Man is involved in the Syndicate, a shadow organization which includes members of the United States government that exists to hide from the public the fact that aliens are planning to colonize Earth.

The Smoking Man often ruthlessly protects the secrets of the conspiracy, and serves as the main antagonist to Mulder, who has an equally consuming devotion to reveal the truth in the first seven seasons.

He is at times shown working towards that goal, particularly in connection with developing a vaccine to protect people from the "black oil", a parasitic agent which the alien Colonists use to propagate themselves.

[21] In at least one early script draft from the "Pilot", a Special Agent named Lake Drazen is present at the meeting near the start of the episode, having chosen Scully for an assignment to evaluate the validity of Mulder's work on the X-Files.

"[23] The Smoking Man is the only character in the series, in addition to Mulder and Scully, to appear in both the first episode, "Pilot" and the last, "The Truth".

Portraying actor William B. Davis was listed as CIA Agent in the first season episode "Young at Heart", instead of his usual character, the Smoking Man.

[25] The character was partly inspired by E. Howard Hunt (1918 - 2007), a CIA operative who was allegedly involved in a range of major conspiracies during the mid-20th century, and who also published a series of espionage novels under multiple pen names.

[34] Likewise, Ken Tucker from Entertainment Weekly felt that "the monotonous evil of Cancer Man" had "become actively annoying" in later seasons of the show, being that his lurking presence did not seem as mysterious anymore.