Hearst is announcing today that Joanna Coles is taking over the top editor spot at Cosmopolitan, replacing Kate White as editor-in-chief. Coles, who has been editor-in-chief at Marie Claire for the last 6 years, will start on September 10.

White, who has been Cosmo’s editor-in-chief since 1998, is stepping down to pursue a writing and speaking career—she’s written the Bailey Weggins mystery series and the recent thriller Hush. She’ll also remain at Hearst in an advisory role.

“Kate is a huge talent who not only maintained Cosmo’s leadership position over the past 14 years but also launched many brand extensions, including Cosmo Radio, bestselling books and a popular tablet edition,” says Hearst Magazines president David Carey in a statement. “She leaves big shoes—or should I say stilettos—to fill and we have no doubt she’ll continue to reach bestseller status in her post-Cosmo career.”

Under Coles, Marie Claire, with a rate base of 950,000 has jumped 19 percent in ad pages for the first half of this year when compared to the same period in 2011, per PIB. Cosmo, with a rate base of 3 million was down slightly by almost 3 percent for the same period.

Helen Gurley Brown, who served as Cosmopolitan’s editor-in-chief from 1965 to 1997 died last month at age 90.

Update: Anne Fulenwider, editor-in-chief of Brides since October 2011, will return to Marie Claire as top editor. She served under Coles as executive editor of MC from 2009 until 2011.