Ms. Bailey, who was the launch editor of Marie Claire in Great Britain in 1988, had been editor in chief of Marie Claire in the U.S. since 1996.
The move comes eight days after Conde Nast Publications sacked Glamour's editor in chief, Bonnie Fuller, replacing her with Self Editor in Chief Cindi Leive.
The Harper's move is another rebutal of Ms. Fuller, who got herself in hot water with her bosses at Conde Nast by repeatedly and publicly promoting herself for the top job at Harper's Bazaar during Ms. Betts' tenure.
Ms. Betts, a protege of Vogue editor Anna Wintour, took over Harper's Bazaar in August 1999, succeeding Liz Tilberis, who died of ovarian cancer. Yet under her regime, Harper's Bazaar still trailed all its main comeptitors -- Hachette Filipachi Magazines Elle, Fairchild Publiscations' W, and Conde Nast Publications' Vogue -- in ad pages, though through April of this year it was the only one of the four to post an ad page gain. For the second half of 2000, according to Audit Bureau of Circulations, newsstand sales dropped 7.4%.
Hearst did not announce a successor to Ms. Bailey at Marie Claire.