Diane Middlebrook, a leading feminist scholar who wrote acclaimed biographies of poets Anne Sexton and Sylvia Plath, died Saturday. She was 68.

Middlebrook helped launch feminist studies at Stanford University in Palo Alto, Calif., where she taught literature for 35 years. She died of cancer in San Francisco, according to Stanford officials.

She is best known for her 1991 bestseller Anne Sexton: A Biography, which was a finalist for the National Book Award, and Her Husband: Ted Hughes & Sylvia Plath, a Marriage, a 2003 bestseller about the tumultuous marriage of the poets.

Middlebrook also wrote Suits Me: The Double Life of Billy Tipton, a 1998 biography about a female jazz musician who lived as a man. A biography about the Roman poet Ovid is expected to be published next year to coincide with the 2,000th anniversary of his birth.

"I think her legacy as a biographer is her incredible humanity," said author Kate Moses, one of many writers and artists encouraged by Middlebrook. "She never sacrificed humanity in maintaining an acute critical recognition of her subject."

Born in Idaho in 1939, Middlebrook grew up in Spokane, Wash., graduated from the University of Washington, Seattle, in 1961 and earned her doctorate at Yale University in 1968. She was among the first women to teach in Stanford's English department.

During her career, she received fellowships from the National Endowment for the Humanities, Bunting Institute at Radcliffe College, Stanford Humanities Center, the John Simon Guggenheim Foundation and the Rockefeller Study Center of Bellagio in Italy.

Survivors include her daughter, two sisters, a stepson, a stepgrandson and her husband, Carl Djerassi, professor emeritus of chemistry at Stanford.