Season 1 of M*A*S*H commenced on 17 September 1972 and consisted of 24 episodes, ending on 25 March 1973. The season developed the characters which had been taken from the movie MASH (1970), in particular highlighting Hawkeye Pierce as the prime character of the ensemble cast. With only one or two possible exceptions (the episodes "Cowboy" and "Showtime"), Hawkeye is either the focus of each story, an agent provocoteur for the events of the story, or else acts as a link between vignette events (as in the "Dear Dad" episodes). The remaining main characters are given greater volition as the season goes on, that is, they are seen to act on their own rather than simply in reaction to something done by Hawkeye or Trapper.
The first episode - Pilot - utilises many, but not all, of the personnel of the 4077th as seen in the first half of the movie. Completely absent are Duke Forrest (Hawkeye's first buddy on the camp before Trapper's arrival) and Staff Sergeant Vollmer (Col.Blake's aide who is regularly outfoxed by Radar). "Painless Pole" Waldowski (the dentist) is mentioned (but not seen) in this episode only. Boone, Lesley Scorch and Ugly John are seen but have no dialogue, "Knocko" McCarthy is portrayed and credited but has no dialogue, and one new character (Ginger) appears and has dialogue in the O.R. and receives a special credit in the final scene.
With those exceptions, the characters adapted from the movie are:
- Captain Benjamin Franklin "Hawkeye" Pierce (played by Alan Alda), the best surgeon in the camp as well as a carouser, trickster and ladies' man. He does not recognise military authority at all - except a certain level of respect for Henry Blake's role as commander of the unit - but does cite his own rank on a couple of occasions to try and coerce a person to change their actions or attitude. Unlike the movie character, Hawkeye in the TV series is a thoracic and general surgeon, and during Season 1 is appointed Chief Surgeon by Blake over and in defiance of the rank of Frank Burns (in the movie it was Trapper who was the chest cutter and Chief Surgeon).
- Captain John "Trapper" McIntyre (played by Wayne Rogers), also an excellent surgeon and Hawkeye's faithful offsider. He is established right from the beginning to be married with children, but is nevertheless Hawkeye's equal in romance and making merry. Whilst he is perfectly capable in his own right of influencing events through deviousness or misdirection, he is most often seen following Hawkeye's lead in the various scams and shenanigans that the two engage in.
- Lt Colonel Henry Blake (played by McLean Stevenson) is another good surgeon, older and more wary than the two captains. He is basically scared of the various Generals to whom he must answer, and completely wrapped around Radar's finger in the administration of the camp. He is also married with children, but has one steady girlfriend at the 4077th (Lesley Scorch). His relationship with the two Majors is testy - he cannot counter Houlihan in military protocol and he has no respect for Burns as a doctor, but remains under the constant threat of them going over his head to a General.
- Major Frank Burns (played by Larry Linville) is a figure of ridicule, portrayed immediately as a blundering or incompetent surgeon at the same time as being a hair-splitter on rank, military discipline and regulations. He is swelled with his own self-importance, derived from his socioeconomic status as a private-practicioner. His religiosity is noted in the series, but toned down from the movie character. Frank's moral duplicity is also highlighted by his licentious relationship with Houlihan, with whom he colludes by day for stricter GI standards around the camp and by night for carnal pleasure.
- Major Margaret "Hot Lips" Houlihan (played by Loretta Swit) is a career Army nurse, swaddled in khaki by her Army father, and is a first-rate officer and medical professional. Her romantic interest in Burns is siutational - they have been thrown together and nobody else in the camp respects the Army the way they do. Nevertheless, it also transpires that Houlihan has "entertained" a wide range of Generals and other officers in her time. Her nickname is a byword at the camp but is also let slip by General Hammond when he sees her in the very first episode. She often acts as the spokesperson when she and Burns jointly present a grievance to Blake.
- Corporal Walter "Radar" O'Reilly (played by Gary Burgoff) is the company clerk, coordinating all administration for the 4077th and acting as Blake's aide-de-camp. His character changes even as the first season develops, beginning as the unflappable problem-solver of the movie but later showing more insecurity and youthful naiveity. His nickname-inspiring characteristic of being able to anticipate events, and particularly Blake's next statement or order, does not change.
- Captain "Ugly" John Black (played by John Orchard) is a specialist aneasthetist, ostensibly from Australia by his accent and slouch-hat uniform. He is part of the friendly cabal of junior male officers but not in the "inner core" with Hawkeye, Trapper and Spearchucker, and does not reside in The Swamp. He is used as a clown character, for example losing continually to Hawkeye at the poker table.
- Captain Oliver "Spearchucker" Jones (played by Timothy Brown) is a specialist neuro-surgeon and, in his brief tenure in the series, a friend on equal terms with Hawkeye and Trapper. He is the only negro officer in the company, which was an historical anomaly and hence the character was dropped after appearing in only three of the first four produced episodes (which were broadcast as the first, 9th and 11th episodes).
- Lieutenant Maggie "Dish" Schneider (played by Karen Phillip), one of the nursing staff, was Hawkeye's love interest in the Pilot but afterwards featured in a very limited role; in particular, Hawkeye was shown consorting with a number of other nurses almost immediately (Margie Cutler in the third, 6th and 7th episodes in particular, although these were produced later in the Season 1 block).
- Ho-Jon (played by Patrick Adiarte) is the Korean "houseboy" for The Swamp (although where he himself resides is never shown). In the TV series he has already been "corrupted" by the junior officers, to the outrage of Burns, and is much more articulate and involved than the same character in the movie. He vanishes from the series before the midpoint of season 1, presumably taking up the offer of a place at Hawkeye's alma mater college (the subject of the pilot episode story).