More than 20 major PR firms that were not in the 2009 O'Dwyer's rankings will be in the 2010 rankings which will be published Monday, March 7.

An improved economy for PR activity is one reason for an increase in the number of rankings, said publisher Jack O’Dwyer.

All 25 of the biggest firms in last year’s rankings have returned for the 2010 rankings, he said.

There will be at least six new firms in the “Top 25,” said O’Dwyer.

Testimony to the effectiveness of the rankings in generating business leads is the 100% return of big firms that are able to supply such information, he said.

Firms that take part in the rankings have greater visibility on Google and in the O’Dwyer website, magazine and newsletter, said O’Dwyer.

“Our rankings are the only ones in the industry based on tax documents, such as top pages of corporate income tax returns and W-3s,” he said. “The business community has come to trust the O’Dwyer rankings which have been done for 40 years.”

The O’Dwyer rankings are also the only ones that provide rankings in specialized categories such as healthcare, tech, financial, food and beauty/fashion, he added.

Firms use their O’Dwyer rankings in their promotions.

“Firms tell us that a ranking helps in attracting good employees since PR pros want to work at a known firm,” said O’Dwyer.

Click here for the ranking form. Deadline for entries is Friday, March 4 at noon. Entries may be e-mailed to [email protected] or faxed to 212/689-6432.