Shareholders of Chicago Mercantile Exchange Holdings and CBOT Holdings voted last night to merge the two largest US futures exchanges.
After an almost nine-month gestation period, the votes delivered one huge, almost $12 billion exchange.
CME Group will be the world's largest derivatives exchange and control more than 85 per cent of US futures and options-on-futures volume.
A competing bid from the upstart Intercontinental Exchange was fended off after CME on Friday improved its bid for a third time since original terms were announced in mid-October.
Preliminary results of separate ballots at each exchange showed an "overwhelming" majority in favour of CME's purchase in a package worth about $11.9 billion, exchange officials said.
Australian investment firm Caledonia Investments, the largest owner of CBOT shares, dropped its opposition to the deal after the terms were improved. At that point many sceptical CBOT member/shareholders also changed their view.
Shareholders of the Chicago Board of Trade's parent will receive 0.375 shares of CME Holdings common stock for each share of CBOT, up from 0.35 in the earlier agreement and 0.3006 when the deal was first announced in October.