| Population Change 1990-2000 | ||||
| County or Municipality | 2000 Population | 1990 Population | Population Change | Percent Change |
| Pennsylvania | 12 281 054 | 11 881 643 | 399 411 | 3.4 |
| Venango County | 57 565 | 59 381 | - 1 816 | - 3.1 |
| Allegheny township | 281 | 281 | 0 | 0.0 |
| Barkeyville borough | 237 | 274 | - 37 | - 13.5 |
| Canal township | 1 008 | 1 067 | - 59 | - 5.5 |
| Cherrytree township | 1 543 | 1 601 | - 58 | - 3.6 |
| Clinton township | 758 | 733 | 25 | 3.4 |
| Clintonville borough | 528 | 520 | 8 | 1.5 |
| Cooperstown borough | 460 | 506 | - 46 | - 9.1 |
| Cornplanter township | 2 687 | 2 968 | - 281 | - 9.5 |
| Cranberry township | 7 014 | 7 256 | - 242 | - 3.3 |
| Emlenton borough | 774 | 824 | - 50 | - 6.1 |
| Franklin city | 7 212 | 7 329 | - 117 | - 1.6 |
| Frenchcreek township | 1 605 | 1 676 | - 71 | - 4.2 |
| Irwin township | 1 309 | 1 182 | 127 | 10.7 |
| Jackson township | 1 168 | 1 089 | 79 | 7.3 |
| Mineral township | 533 | 514 | 19 | 3.7 |
| Oakland township | 1 565 | 1 527 | 38 | 2.5 |
| Oil City city | 11 504 | 11 949 | - 445 | - 3.7 |
| Oilcreek township | 840 | 915 | - 75 | - 8.2 |
| Pinegrove township | 1 338 | 1 395 | - 57 | - 4.1 |
| Pleasantville borough | 850 | 991 | - 141 | - 14.2 |
| Plum township | 1 060 | 1 031 | 29 | 2.8 |
| Polk borough | 1 031 | 1 267 | - 236 | - 18.6 |
| President township | 543 | 501 | 42 | 8.4 |
| Richland township | 744 | 775 | - 31 | - 4.0 |
| Rockland township | 1 346 | 1 320 | 26 | 2.0 |
| Rouseville borough | 472 | 583 | - 111 | - 19.0 |
| Sandycreek township | 2 406 | 2 495 | - 89 | - 3.6 |
| Scrubgrass township | 799 | 673 | 126 | 18.7 |
| Sugarcreek borough | 5 331 | 5 532 | - 201 | - 3.6 |
| Utica borough | 211 | 242 | - 31 | - 12.8 |
| Victory township | 408 | 365 | 43 | 11.8 |
| Source: U.S. Census Bureau | Prepared by: Pennsylvania State Data Center | |||