Thompson adopted the Rastafarian faith at an early age. He honed his talents on local sound systems such as Coxsone Dodd's Downbeat and Lord Tippertone, and started to record very young under various names (Winston Price, Winston Cool, Ital Winston, or Youth Winston). His first recordings were for Lee "Scratch" Perry and Bunny Lee - "Place Called Africa Version 3" and "Maccabee Version". He returned to Lee "Scratch" Perry in 1976, recording the DJ portion of Devon Irons' 12" "Ketch Vampire". Between 1971 and 1977 his singles were unreleased outside Jamaica, only being available in the UK on import. He built his reputation with tunes such as "Oil Crisis" (versioning Horace Andy's "Ain't No Sunshine"), "Sons of Thunder", (toasting over Jackie Brown's "Wiser Dread"), "Gimme Mi Gun" on Gregory Isaacs' "Thief a Man" and "Poison Flour", on a recut of The Paragons "Man Next Door" rhythm. He mainly met success in the mid to late 1970s, with his best-known album being Best Dressed Chicken in Town (1978), a Greensleeves Records collection of tracks recorded in the mid-70s, featuring Alimantado toasting over singers such as John Holt, Gregory Isaacs, Jackie Edwards and Horace Andy. His tunes mixed his Rastafari movement beliefs with commentary on events then going on in his community; "Poison Flour" referenced a January 1976 incident when 79 persons in Jamaica were acutely poisoned by consuming flour contaminated by leakage of the insecticide parathion in a ship's hold. Seventeen died.
Alimantado became popular with punk rockers in the 1970s following Johnny Rotten praising him in an interview. He was mentioned in the 1979 song "Rudie Can't Fail" by The Clash in the line "Like the doctor who was born for a purpose". The artist recorded "Born for a Purpose" in 1977 at Channel One, one of Alimantado's biggest hits (along with "A Place Called Africa"). "Born for a Purpose" was originally released on his Vital Food label, and told of his Rastafarian faith supporting him after bus driver had driven into him in Kingston on 26 December 1976, causing serious injuries. The musicians who played on the record did so without payment. The single, and its accompanying version "Still Alive" were released in the UK firstly as two 7" 45s, then as a 12", featuring the full extended mixes. By 1977 he had largely abandoned his toasting style, apart from occasional records such as "Go Deh Natty Go Deh" on a heavily dubbed mix of Delroy Wilson's "Trying to Conquer Me", preferring to release singing tunes, including "Mama (I Thank You)", "Jah Love Forever", and a cover of Billy Stewart's "Sitting in the Park".
Following the success of Best Dressed Chicken and its follow-up compilation Sons of Thunder he signed to Virgin Records as a singer. While not without vocal talent, his singing records never captured the public imagination to the extent that his "toasting" records did.
The film Hancock featured the song "Best Dressed Chicken in Town".
2009 marked the 30th anniversary of his album Best Dressed Chicken in Town. To mark the occasion Alimantado re-released the album in its original sleeves with a bonus DVD on his own Keyman Records label.