| Company | Product/Service | Employment |
| Mercy Health System | Medical Services | 3,688 |
| General Motors | Trucks, SUVs | 2,800 |
| Janesville School District | Public Education | 1,510 |
| Rock County | Government | 1,181 |
| Beloit School District | Public Education | 1,153 |
| Beloit Memorial Hospital | Medical Services | 1,063 |
| Lear Corporation | Motor vehicle seating | 947 |
| Lab Safety Supply, Inc. | Catalog distributor - safety supplies | 795 |
| Blackhawk Technical College | Education & Training | 770 |
| Frito-Lay | Snack Foods | 750 |
| SSI Technologies | Automobile control devices | 723 |
| Wal-Mart | Retail Department Store | 662 |
| ABC Supply Co. | Wholesale Construction Materials & Tools | 600 |
| Lemans Corporation | Distributor - recreational vehicles, etc. | 500 |
| Woodman's Food Market, Inc. | Supermarkets | 490 |
| City of Janesville | Government | 484 |
| Beloit College | Liberal arts college | 470 |
| Dean Riverview Clinic | Medical Services | 440 |
| Kerry Ingredients | Dehydrated food products | 421 |
| Alcoa Wheel International | Aluminum wheels | 414 |
| Goodrich Corporation | Diesel engines & accessories | 400 |
| Prent Corporation | Custom thermoformed plastic parts | 400 |
| Seneca Foods Corporation | Vegetable / Foods Processing | 400 |
| City of Beloit | Government | 399 |
| Gilman Engineering | Automated assembly & product machinery | 380 |
| Hufcor, Inc. | Accordion doors & walls | 345 |
| Regal-Beloit Corporation | Cutting tools, power trans. equipment | 340 |
| Chambers & Owen | Wholesale merchandise | 325 |
| Edgerton Hospital & Health Services | Medical Services | 310 |
| J.P. Cullen & Sons | Construction | 310 |
| Beloit Clinic | Medical Services | 300 |
| Varco Pruden Corporation | Pre-engineered metal buildings | 300 |
| Hormel | Canned meat products | 265 |
| Baker Manufacturing | Water & oil well equipment | 260 |
| Alliant Energy | Utilities | 260 |
| Stoughton Trailers | Chassis & Containers | 250 |
| United Industries | Stainless steel tubing | 200 |
| Swing 'N' Slide | Swingset & metal fabricated products | 190 |