"One of Us Must Know (Sooner or Later)" is a song written and recorded by Bob Dylan. It is the fourth track on his 1966 album Blonde on Blonde, and was released as the album's first single that February. The song is an emotional confession of misconnects and apologies from the singer to a woman who has tragically slipped out of his life. As a single, it peaked at No. 33 in the UK Singles Chart, but only reached No. 119 on US Billboard's Bubbling Under chart.

According to Jonathan Singer, it was Paul Griffin who played the piano part on "One of Us Must Know (Sooner or Later)".

A Phil Spector styled cover of this song was released by Les Fradkin on If Your Memory Serves You Well (2006).

English singer-songwriter Mick Hucknall covered the song on the 2012 charity compilation album Chimes of Freedom: The Songs of Bob Dylan Honoring 50 Years of Amnesty International.

Musically, the track is typical of the album: a treble single coil guitar adds a base to the song with the acoustic and bass while organs and pianos take the lead in forming the song. Jazz style drumming is used effectively.

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