The 2010 Inc. 500|5000 is ranked according to percentage revenue growth from 2006 through 2009. To qualify, companies must have been founded and generating revenue by June 30, 2006. Additionally, they had to be based in the United States, privately held, for profit, and independent—not subsidiaries or divisions of other companies—as of December 31, 2009. (Since then, a number of companies on the list have gone public or been acquired.)

The minimum revenue required for 2006 is $80,000; the minimum for 2009 is $2 million. Revenue figures given in the company profiles are for calendar year 2009, as are employee counts. Full-time and part-time employees are included in the employee counts; independent contractors are not.

Two Inc. 500-level companies, Octo Consulting and Virtualosity Solutions, came to Inc.'s attention past the deadline for the print edition. They have been listed as ties at No. 23 and No. 160 respectively on the online Inc. 500|5000.
As always, Inc. reserves the right to reject applicants for subjective reasons.