| Abbreviation | Definition |
|---|---|
| PNR | PentAir, Inc. |
| PNS | Pinnacle Data Systems |
| PNU | Pharmacia & Upjohn, Inc. |
| PNW | Pinnacle West Capital Corporation |
| PNX | The Phoenix Companies, Inc. |
| PNX | The Phoenix Companies, Incorporated |
| PNY | Piedmont Natural Gas, Inc. |
| POB | Philadelphia, Pennsylvania, Authority for Industrial Development |
| POFE | Port Of First Entry |
| POG | Patina Oil & Gas Corporation |
| POI | Protection One, Inc. |
| POL | PolyOne Corporation |
| POM | Potomac Electric Power Company |
| POMPT | Potomac Electric Power Company Trust I |
| POP | Pope & Talbot, Inc. |
| POP | Pope & Talbot, Incorporated |
| POR | Poor and Company (now delisted) |
| POR | Portec |
| POS | Catalina Marketing Corporation |
| POT | POTASH Corporation of Saskatechewan, Inc. |