She was born Kathrina E. Klotz on October 28, 1920, in Brooklyn, New York. The first of the 60 Broadway productions on which she worked was the original production of The King and I (1951), for which she assisted Irene Sharaff. In the early years of her career, she also frequently assisted another famous Broadway costumer, Lucinda Ballard.
In 1972 and 1973, Klotz won back-to back Tony Awards for her costume designs for the Stephen Sondheim-Hal Prince musicals Follies and A Little Night Music. Her third Tony came in 1976 for yet another Sondheim-Prince show, Pacific Overtures. She also won Tonys for Grind, Kiss of the Spider Woman, and Prince's 1994 revival of Show Boat. Her other Broadway credits include On the Twentieth Century, City of Angels, It's a Bird...It's a Plane...It's Superman, Rags, and the 1981 production of The Little Foxes that starred Elizabeth Taylor.
Klotz received an Academy Award nomination for her work on Prince's film version of A Little Night Music, which also starred Taylor; and she designed the costumes for the only other film directed by Prince, Something for Everyone, which starred Angela Lansbury. Additionally, she costumed several ballets that were choreographed by Jerome Robbins, the Chicago Lyric Opera production of Madama Butterfly, and John Curry's Symphony on Ice. She also designed Elizabeth Taylor's ensemble for her 1976 wedding to Senator John Warner.
In addition to her Tonys, Klotz won five Drama Desk Awards, three L.A. Critic Circle Awards, and two Outer Critics' Circle Awards. In 2002, she received the Patricia Zipprodt Award from the Fashion Institute of Technology; and in 2005, she won the Irene Sharaff Lifetime Achievement Award.
Among her survivors are her niece, Suzanne DeMarco, and her cousin Paula Silbert. No ceremony will be held; those who wish to memorialize Klotz are asked to make donations to Broadway Cares/Equity Fights AIDS.