| Abbreviation | Definition |
|---|---|
| AT | Alltel Corporation |
| ATC | Cycle Country Accessories Corporation |
| ATG | A G L Resources, Inc. |
| ATG | AGL Resources, Incorporated |
| ATI | Allegheny Technologies, Inc. |
| ATK | Alliant Techsystems, Inc. |
| ATL | Atalanta Sosnoff Capital Corporation |
| ATLS | Atlas Energy, L.P., Common Units |
| ATN | Action Performance Companies |
| ATO | Atmos Energy Corporation |
| ATR | Aptar Group, Inc. |
| ATS | A P T Satellite Holdings, LTD. |
| ATW | Atwood Oceanics, Inc. |
| ATY | Gurpo Casa Autrey S. A. de C. V. |
| AU | AngloGold Ashanti, LTD. |
| AUBJ | PowerOptions Option Call February 2008 |
| AUD | Automatic Data Processing |
| AVA | Avista Corporation |
| AVAPA | Avista Capital I |
| AVAPL | Avista Corporation Preferred L |