It sounds like hyperbole to claim that this year's list of the Top 100 Washington businesses is bigger and better than ever, but it's true.

Bigger, because the listing has been expanded to include the 100 largest publicly owned companies in the greater Washington area. The biggest private companies in the metropolitan area and the biggest businesses in out-state Maryland and Virginia are ranked separately this year.

Better, because in addition to the traditional top 100 firms, this year's census for the first time counts many of the other companies that contribute to the regional economy.

What's new is a compilation of the 10 largest local employers who are not based in the District, Maryland or Virginia. Companies like IBM--with some 10,000 Washington area workers--aren't usually counted in the census of Washington Business because IBM's headquarters is in New York.

American Telephone & Telegraph Co. had never counted up its local employes until asked to do so. The 5,000 AT&T people working here are in addition to the thousands employed by C&P Telephone Co., which will be a totally separate company by the end of the year when the AT&T divestiture is completed.

Adding up all these companies produces what we call The Post 100+. It's the top 100 public companies in the local region, plus the top 10 in Virginia and Maryland, plus the biggest out-of-town employers plus the biggest private firms.

Ranking the top companies is not just a matter of lining up 100 annual reports, with $7.2 billion-a-year Federal National Mortgage Association on one end and $4.16 million Isomet Corp. on the other.

First you have to decide how to rank them--biggest in revenues, biggest in assets, biggest in employes? Ranked by employes alone, McDonald's would be one of the biggest out-of-town companies in Washington, but the overwhelming majority of those people are part-timers, so McDonald's didn't qualify.

Revenues and assets are the traditional measure of size. By both criteria, FNMA is the biggest business in town with revenues of $7.2 billion and assets of $73.5 billion.

But those two yardsticks don't accurately measure all businesses.

Comparing financial institutions with manufacturers, retailers or technology companies on the basis of assets can be extremely misleading. Dart Drug, with more than a hundred stores and thousands of employes, is one of the area's oldest and largest retailers, but its $118 million in assets are only a few million dollars more than those of tiny Burke & Herbert Bank. And it took Geico Corp. less than a year to build the assets of its money market fund to $100 million.

Ranking by assets not only tilts the list in favor of financial institutions, it underrates high-technology and research firms. Their true value is not bricks and mortar but intangibles that aren't reflected on the balance sheet.

On the other hand, using revenues to judge size works against financial institutions. A retailer counts as revenues every dollar that goes in the cash drawer, but banks don't do that. Ranked by revenues, Maryland National Bank, biggest in the region, wouldn't make the top 25 companies.

To avoid such misleading distortions, which are common to many corporate rankings, firms in The Post 100+ are ranked in two separate groups. The 25 largest financial institutions are listed by assets; the 75 nonfinancial companies (everybody else) are rated by revenues, with a separate chart showing how they'd rank on the basis of assets.

The Post 100+ is unique also in its emphasis on Washington business--the companies Washington-area residents are most likely to invest in, work for and do business with.

Starting with Securities and Exchange Commission filings of all the more than 200 stockholder-owned companies in the District of Columbia, Maryland and Virginia, the list was pruned to companies in the Washington area. Defining the "Washington market" is so complex that the Census Bureau is struggling with a new definition, but companies from Baltimore, Richmond and beyond clearly aren't Washington businesses. The list does reach beyond the beltway to pick up the likes of O'Sullivan Corp. in Winchester, Pargas in Waldorf and Preston Trucking in Easton.

The only exception to the geographic guideline involves the big Virginia and Maryland banks that dominate banking in the Washington suburbs. They are as much a part of the Washington financial community as Riggs or American Security.

The gigantic job of reporting on this multibillion-dollar business network was shared by a team of Washington Post staff reporters, editors, researchers and special assignment writers. Researcher Mark Murphy managed the massive data collection and analysis job. Post reporters provided updated details on the bigger firms that are part of their regular beats. Special writers John Dougherty, Paul Goldberg and Linda Keslar profiled the remaining companies.

Their work adds up to the most ambitious--and hopefully most accurate--portrait ever painted of the extraordinarily healthy Washington business family.