| Type | Prefix | Notes |
|---|
| B & O Railroad Museum | BO | |
| Baltimore 4 Wheelers, Inc. | BW | |
| Baltimore American Indian Center, Inc. | AI | |
| Baltimore Area Alumni Association, Inc. of Alpha Phi Omega fraternity | MS | |
| Baltimore Bicycling Club, Inc. | BBC | Non-logo |
| Baltimore Blues Society | BBS | |
| Baltimore City College Alumni Association, Inc. | BCC | |
| Baltimore City Community College | BCO | Non-logo |
| Baltimore City Fire Department | BFS | |
| Baltimore City Fire Fighters Local No. 734 | FL | |
| Baltimore City Fire Fighters Local No. 734 – motorcycle | FL suffix | |
| Baltimore City Fire Officers – motorcycle | FO suffix | |
| Baltimore County Fire Department Chief Officers Association, Inc. | FX | |
| Baltimore County Fire Fighters Association Local No. 1311 | CF | |
| Baltimore County Fire Fighters Association Local No. 1311 – motorcycle | CF suffix | |
| Baltimore County Retired Fire Officers and Fire Fighters | RS | |
| Baltimore Duckpin Bowlers Association | BD | |
| Baltimore Fire Officers Association | FO | |
| Baltimore Kickers, Inc. | KX | |
| Baltimore Metro Chapter of the Harley Owners Group, Inc. | HD | |
| Baltimore Metro Chapter of the Harley Owners Group, Inc. – motorcycle | HD suffix | |
| Baltimore Polytechnic Institute Alumni Association | BPI | |
| Baltimore Professional Duckpin Association | BPD | Non-logo |
| Baltimore Retired Police Benevolent Association | BRP | |
| Baltimore Ski Club, Inc. | SKI | |
| Baltimore Streetcar Museum, Inc. | BSM | |
| Baltimore Symphony Associates | BSO | |
| Baltimore Teachers Union | BTU | |
| Baltimore Tuskegee Alumni Association | TU | |
| Baltimore Washington Conference of United Methodist Men | BWC | |
| Baltimore Yacht Club | BYC | |
| Bay District Volunteer Fire Department | BD | |
| Bel Air Corvette Club | BAC | |
| Bel Air Volunteer Fire Company, Inc. | VFC | |
| Bel Alton Volunteer Fire Department, Inc. | BA | |
| Benedict Volunteer Fire Department & Rescue Squad, Inc. | BFR | |
| Berlin Fire Company, Inc. | BF | |
| Berwyn Heights Volunteer Fire Department and Rescue Squad, Inc. | TS | |
| Birds of Prey the Chamber of Baltimore Ravens Nest, Inc. | BOP | |
| Bishop Episcopal Diocese of Easton | EC | |
| Bishop Walsh School | BWS | |
| Bishopville Volunteer Fire Department, Inc. | BV | |
| Bladensburg Volunteer Fire Department and Rescue Squad, Inc. | BFD | |
| Blue Knights International Law Enforcement Motorcycle Club, Inc. | BK | |
| Blue Knights International Law Enforcement Motorcycle Club, Inc. – motorcycle | BK suffix | |
| Blue Star Mothers | MBS | |
| BMW Bikers of Metropolitan Washington | BMR suffix | |
| BMW (Car) Owners' Club | BMW | |
| Boonsboro Athletic Boosters, Inc. | BHS | |
| Boumi Temple A.A.O.N.M.S. | BB | |
| Bowie State University Alumni | BSU | |
| Bowie Volunteer Fire and Rescue, Inc. | RF | |
| Box 414 Association, Inc. | BX | |
| Boy Scouts of America | BSA | |
| Boys' Latin School of Maryland, Inc. | BL | |
| Brandywine Volunteer Fire Department | BVF | |
| Bread of Life Tabernacle | BOL | |
| Brunswick Volunteer Ambulance & Rescue, Inc. | BVA | |
| Bryans Road Volunteer Fire Department and Rescue Squad | BR | |
| Bryn Mawr School | BMS | |
| Building Industries Foundation | HBA | |
| Burtonsville Volunteer Fire Department, Inc. | BM | |
| Bush River Yacht Club | BRY | |
|
