There are four businesses with fewer than 500 employees (the SBA's technical definition of a "small" business) that are listed on the Fortune 1000:

• Number 999 by the number of employees. One of the highest dollar volume-to-employees ratios, World Fuel Services Corporation is Number 994 on the Fortune 1000 index by sales volume.. They are located in Miami Springs, FL 33166 http://www.wfscorp.com With 2001 sales of over $1,500,000,000, they did it with just 181 to 243 employees.
• Number 997 is Priceline.com (981 on the Fortune 1000) with $1,235B in sales with 370 employees.
• Number 998 is D & K Healthcare Resources (891 on the Fortune 1000) with $1,450B in sales with 334 employees.
• Number 1,000 with the fewest employees of a Fortune 1000, is Host Marriott, Number 882 with $1,420B in sales with 215 employees. Reports Hoovers: "...the largest hotel real estate investment trust (REIT) in the U.S."

Hoovers Online at http://hoovers.com is a good resource for employee numbers.

Medium-sized businesses employ between 500 and 5000 people. Big business employs over 5000. IBM employs over 300,000. The USPS employs over 900,000.

We have also begun researching the number of small businesses with the Fortune 1000 to 2000. Somewhere around the Fortune 1500, the number of employees consistently drops below the 500 mark.

There are over 9M small businesses with between 2 and 5 employees.