Deal making has always been what makes the commercial real estate industry go round, but the volume of mergers and acquisitions over the past 12 months has an unprecedented fever-pitch quality to it.

Thanks to competitively priced debt financing and high demand for assets, property sales reached a record $355 billion in 2006, according to Real Capital Analytics, which tracks transactions $5 million and higher. Through May of this year, a whopping $241 billion worth of assets had traded hands.

The deal of all deals — - Blackstone Group's leveraged buyout of Equity Office Properties (EOP) for $39 billion — added an exclamation point to the privatization wave sweeping over the industry. That deal closed earlier this year.

Not only had giant EOP become the largest real estate investment trust by market cap since going public in July 1997, it also was the first REIT to be included in the S&P 500 four years later. But that's now a distant memory.

As huge portfolios continue to be ushered off the public stage only to be liquidated piecemeal, determining who owns what has become increasingly complex. Firms like The Blackstone Group are mum on their real estate holdings. Conservative estimates peg the liquidation value of its global real estate holdings at roughly $46 billion.

In this special section, NREI ranks the largest companies in the industry across several property sectors and disciplines. All totals are as of Dec. 31, 2006.

Only the top 25 companies in each category appear in print. A complete listing of the totals will appear online. The ranking of top shopping center owners was originally published in NREI's sister publication, Retail Traffic. The apartment ranking was tabulated by the National Multi Housing Council and first printed in NREI in April.