Sheets of Bulgaria, 1991
| Issuer | Date | Desc | State | ||
| - | no image | Bulgaria | 3/19/1991 | Poisonous Mushrooms, sheet of 1 type | incomplete |
| - |  |
Bulgaria | 4/1/1991 | empty sheet (#6258) | incomplete |
| - |  |
Bulgaria | 7/23/1991 | 10th anniversary of the Space Shuttle, sheet of 1 type | all added |
| - |  |
Bulgaria | 7/23/1991 | 10th anniversary of the Space Shuttle, sheet of 1 type | all added |
| - |  |
Bulgaria | 8/7/1991 | Winter Olympics 1992, sheet of 1 type | all added |
| - |  |
Bulgaria | 8/7/1991 | Winter Olympics 1992, sheet of 1 type | all added |
| - | no image | Bulgaria | 10/11/1991 | empty sheet (#83454) | incomplete |
| - | no image | Bulgaria | 10/21/1991 | empty sheet (#83455) | incomplete |
| - |  |
Bulgaria | 10/23/1991 | 200 Years Brandenburg Gate, sheet of 1 type | all added |
| - |  |
Bulgaria | 10/23/1991 | 200 Years Brandenburg Gate, empty sheet (#6265) | incomplete |
| - | no image | Bulgaria | 11/11/1991 | empty sheet (#83456) | incomplete |
| - |  |
Bulgaria | 12/13/1991 | 450th Birth anniversary of El Greco, sheet of 1 type | all added |