He is universally known as the activist who championed the rights of black people - but a new book also claims Malcolm X was bisexual who had an affair with a white man.
The book, written by one of New York's foremost African-American scholars, says Malcolm X had a relationship with a white businessman.
The bisexual claims are sure to re-ignite the controversy first stirred in a 1991 biography that detailed Malcolm X's alleged gay experiences.
The new book, Malcolm X: A Life of Reinvention by Manning Marable, also claims that one of the men who assassinated Malcolm X escaped justice and is alive and well.
Two men were wrongly convicted of his murder in 1965 - and one of the real gunmen still lives in the New York area, Mr Marable wrote.
Malcolm X was gunned down as he gave a speech in the Audubon ballroom in Manhattan by one man with a shotgun and two others with pistols.
X famously said that the struggle for African American freedom should be achieved by 'any means necessary' - rather than the peaceful protest of Martin Luther King.
He rose to prominence as spokesman for the Nation of Islam church before becoming disillusioned and splitting with its leaders. He was immortalised in Alex Haley's book The Autobiography of Malcolm X and a 1992 film by Spike