When the results of The National Law Journal‘s 21st annual Who Represents Corporate America survey came in this summer, one thing was immediately clear: Workplace issues were among companies’ biggest concerns. Law firms that did a substantial amount of labor and employment litigation work for big companies in 2007 had the most mentions.

The evidence? Morgan, Lewis & Bockius took the No. 1 spot, with half of the matters captured in our survey related to employment and labor. Littler Mendelson, the largest U.S. law firm devoted exclusively to representing management in employment matters, tied for the silver.

There are several factors at play, say attorneys and consultants. Workplace-related suits are now driving many corporate legal budgets. According to the Washington-based Federal Judicial Center, labor class actions have quadrupled since 2001.

“For some of these companies, it’s the single most significant legal exposure they’ve ever had,” said Marko Mrkonich, the managing director and president of Littler Mendelson.

But companies are also consolidating their labor and employment law portfolios and hiring fewer firms, said Newport Beach, Calif., legal consultant Peter Zeughauser. “It’s been going on for a number of years,” Zeughauser said. “And now it’s starting to show up in the statistics.”

To get a more accurate picture of which top firms are called on the most, we refined our methodology for this year’s survey. Last year, we used court and agency records to see which firms the Fortune 250 used most in 2006 in just four legal areas: commercial law and contracts litigation; corporate transactions; labor and employment litigation; and IP litigation and patent prosecution.

With the current survey, we both narrowed and deepened its scope. While we focused only on the Fortune 100 companies, we looked at their subsidiaries for the first time. We added a new practice area, torts and negligence, and we also expanded our patent prosecution research.

Last year, we looked at data for patents granted the previous year. This year, we looked at data for both granted patents and patent applications in both 2006 and 2007 because the patent-granting process takes, on average, more than a year.

Then we tallied the number of mentions each firm received. Firms used for litigation had to be mentioned at least twice to make our most-mentioned list. Obviously, however, much of the work done for corporate legal departments never sees the inside of a courtroom, so our emphasis on court filings limits how many times some firms appear.

As a result, we have more complete data for the companies we surveyed — and a more complete picture of the top go-to firms.

Most-mentioned law firms

Despite all these changes, familiar faces abound. Littler Mendelson, with 24 mentions, tops the employment and labor litigation list, just as it did last year. Ogletree, Deakins, Nash, Smoak & Stewart was close behind, with 20.

 Once again, New York-based Skadden, Arps, Slate, Meagher & Flom is the lead firm for corporate transactions, with 14 mentions. Davis Polk & Wardwell came in second, with 10.

Greenberg Traurig leads in commercial law and contracts litigation, with six mentions, followed by three firms tied with five: Day Pitney and two small firms specializing in debt collection, Eichenbaum & Stylianou of Paramus, N.J., and Goldman & Warshaw of Pine Brook, N.J.

Shook, Hardy & Bacon topped our new torts and negligence practice area with eight mentions, just ahead of Baker, Donelson, Bearman, Caldwell & Berkowitz and Reed Smith, with seven apiece.

One surprise: For IP work, boutiques like Fish & Richardson no longer dominate. Instead, megafirms Jones Day and Baker Botts top the list with 12 mentions each. Close behind are Howrey of Washington and McDermott, Will & Emery, each with 11.

But all of these changes are fairly minor, and they offer an unarguable truth: No matter how we slice the data, when trouble looms, America’s largest companies call on the same small group of big firms they trust most.

COMPANIES LISTED

3M Co. [100]
AT&T Inc. [10]
Abbott Laboratories [96]
Aetna Inc. [85]
Alcoa Inc. [80]
The Allstate Corp. [64]
Altria Group Inc. [61]
American Express Co. [75]
American International Group Inc. [13]
Amerisource-Bergen Corp. [28]
Archer Daniels Midland Co. [52]
Bank of America Corp. [9]
Berkshire Hathaway Inc. [11]
Best Buy Co. Inc. [66]
The Boeing Co. [27]
CVS Caremark Corp. [24]
Cardinal Health Inc. [19]
Caterpillar Inc. [50]
Chevron Corp. [3]
Cisco Systems Inc. [71]
Citigroup Inc. [8]
The Coca-Cola Co. [83]
Comcast Corp. [79]
ConocoPhillips [5]
Costco Wholesale Corp. [29]
Dell Inc. [34]
Delphi Corp. [92]
The Dow Chemical Co. [42]
E.I. du Pont de Nemours and Co. [81]
Enterprise GP Holdings L.P. [90]
Exxon Mobil Corp. [2]
Federal Home Loan Mortgage Corp. [54]
Federal National Mortgage Association [53]
FedEx Corp. [68]
Ford Motor Co. [7]
GMAC LLC [78]
General Dynamics Corp. [87]
General Electric Co. [6]
General Motors Corp. [4]
The Goldman Sachs Group Inc. [20]
HCA Inc. [89]
The Hartford Financial Services Group Inc. [95]
Hess Corp. [77]
Hewlett-Packard Co. [14]
The Home Depot Inc. [22]
Honeywell International Inc. [73]
Humana Inc. [98]
Ingram Micro Inc. [69]
Intel Corp. [60]
International Business Machines Corp. [15]
JPMorgan Chase & Co. [12]
Johnson & Johnson [35]
Johnson Controls Inc. [72]
Kraft Foods Inc. [63]
The Kroger Co. [26]
Lehman Brothers Holdings Inc. [37]
Liberty Mutual Holding Co. Inc. [94]
Lockheed Martin Corp. [57]
Lowe’s Cos. Inc. [48]
Macy’s Inc. [91]
Marathon Oil Corp. [36]
Massachusetts Mutual Life Insurance Co. [99]
McKesson Corp. [18]
Medco Health Solutions Inc. [51]
Merrill Lynch & Co. Inc. [30]
MetLife Inc. [43]
Microsoft Corp. [44]
Morgan Stanley [21]
Motorola Inc. [65]
New York Life Insurance Co. [82]
News Corp. [84]
Northrop Grumman Corp. [76]
PepsiCo Inc. [59]
Pfizer Inc [47]
The Procter & Gamble Co. [23]
Prudential Financial Inc. [74]
Safeway Inc. [55]
Sears Holdings Corp. [45]
Sprint Nextel Corp. [58]
State Farm Mutual Automobile Insurance Co. [32]
Sunoco Inc. [56]
Supervalu Inc. [62]
Sysco Corp. [70]
Target Corp. [31]
Teachers Insurance and Annuity Association-College Retirement Equities Fund [86]
Time Warner Inc. [49]
The Travelers Cos. Inc. [93]
Tyson Foods Inc. [88]
United Parcel Service Inc. [46]
United Technologies Corp. [39]
UnitedHealth Group Inc. [25]
Valero Energy Corp. [16]
Verizon Communications Inc. [17]
Wachovia Corp. [38]
Walgreen Co. [40]
Wal-Mart Stores Inc. [1]
The Walt Disney Co. [67]
Washington Mutual Inc. [97]
WellPoint Inc.[33]
Wells Fargo & Co. [41