Catherine Marshall LeSourd, 68, the author of "A Man Called Peter," a best-selling biography about her first husband, the Rev. Peter Marshall, that was made into a successful film, died March 18 at a hospital in Boynton Beach, Fla., after a heart attack. She lived on a farm in Lincoln, Va.

Mrs. Marshall, as she was known professionally, and the Rev. Marshall were married in 1936 and moved to Washington five years later. The Rev. Marshall was pastor of New York Avenue Presbyterian Church and chaplain of the Senate from 1947 until his death in 1949.

Mrs. Marshall compiled a book of his sermons, "Mr. Jones, Meet the Master." She published "A Man Called Peter" in 1951. The film based on it was released by Twentieth Century-Fox in 1955 and was the studio's biggest hit that year.

In 1959, she married Leonard E. LeSourd, editor of Guideposts, a magazine published by the Rev. Dr. Norman Vincent Peale. Her works always had inspirational themes, whether they were fiction, biography, autobiography or collections of meditations. Her 18 books sold more than 18 million copies in 35 languages.

They included "Christy," a novel about a young mountain schoolteacher that was partially based on the life of her mother; "The Unwilling Heart," a novel for teen-agers dealing with racial prejudice; and "God Loves You," a collection of religious essays for children. She also wrote her autobiography, "Meeting God At Every Turn."

Mrs. Marshall's last two books, "The Best of Peter Marshall," and a novel, "Watershed," a story set in the 1930s, are scheduled to be published soon.

She was born in Johnson City, Tenn., the daughter of a Presbyterian minister. She graduated Phi Beta Kappa from Agnes Scott College in Decatur, Ga. She had been an editor of Guideposts magazine since 1961.

In addition to her husband, of Lincoln, survivors include one son by her first marriage, the Rev. Peter J. Marshall of Orleans, Mass.; three children by her second marriage, Chester LeSourd of Chattanooga, Tenn., Jeffrey LeSourd of St. Louis, and Linda LeSourd Lader of Hilton Head Island, S.C.; her mother, Leonora Wood of Lincoln; a sister, Emma Hoskins of Mountain Home, N.C., and five grandchildren.