New York--OgilvyOne has named Brian Fetherstonhaugh CEO, effective in October, to succeed current CEO Reimer Thedens. Thedens will remain as chairman of OgilvyOne until his retirement in 2005. Fetherstonhaugh is currently chairman of global brands for Ogilvy & Mather Worldwide. John Seifert will succeed Fetherstonhaugh as chairman of global brands. He is currently global leader for American Express Co., BP and Du Pont at Ogilvy & Mather Worldwide.