EQUITY OFFICE PROPERTIES TRUST (turnover $1.7 billion in 1998), the leading American company for office real estate, has made a friendly bid of $4.6 billion (comprising takeover of debts amounting to 1.8 billion) on its compatriot CORNERSTONE PROPERTIES (turnover $359 million in 1998). The transaction will take place partly through an exchange of shares (55%) and the rest in liquid, at the price of $18 per share on average.