| 1199SEIU in Frederick, MD | AMERIGROUP in Frederick, MD |
| APS Healthcare in Frederick, MD | Aetna in Frederick, MD |
| Alliance in Frederick, MD | AmeriHealth in Frederick, MD |
| American Behavioral in Frederick, MD | Beech Street in Frederick, MD |
| Behavioral Health Systems in Frederick, MD | BlueCross and/or BlueShield in Frederick, MD |
| CCN in Frederick, MD | CHIPA/College Health in Frederick, MD |
| Cascade Health in Frederick, MD | Ceridian in Frederick, MD |
| ChoiceCare in Frederick, MD | Cigna in Frederick, MD |
| ComPsych in Frederick, MD | Corphealth in Frederick, MD |
| Coventry in Frederick, MD | First Choice Health in Frederick, MD |
| First Health in Frederick, MD | GHI/Group Health Incorporated in Frederick, MD |
| Great-West in Frederick, MD | Guardian in Frederick, MD |
| HFN in Frederick, MD | HIP/Health Plan of New York in Frederick, MD |
| Harvard Pilgrim Health Care in Frederick, MD | Health Net in Frederick, MD |
| Holman Group in Frederick, MD | Horizon Healthcare in Frederick, MD |
| Humana in Frederick, MD | Integrated Health Plan in Frederick, MD |
| Interplan in Frederick, MD | Kaiser in Frederick, MD |
| LifeWise in Frederick, MD | MAMSI in Frederick, MD |
| MHN/Managed Health Network in Frederick, MD | Magellan Behavioral Health in Frederick, MD |
| MagnaCare in Frederick, MD | Medica in Frederick, MD |
| Medicaid in Frederick, MD | Medical Mutual in Frederick, MD |
| Medicare in Frederick, MD | Multiplan in Frederick, MD |
| NCPPO in Frederick, MD | ODS in Frederick, MD |
| Oxford in Frederick, MD | PHCS/Private Health Care Systems in Frederick, MD |
| PPOM in Frederick, MD | PacifiCare in Frederick, MD |
| PacificSource in Frederick, MD | PreferredOne in Frederick, MD |
| Providence in Frederick, MD | Sloans Lake in Frederick, MD |
| TRICARE in Frederick, MD | TriWest0127 in Frederick, MD |
| Tufts in Frederick, MD | UniCare in Frederick, MD |
| Uniform in Frederick, MD | United in Frederick, MD |
| VMC in Frederick, MD | ValueOptions in Frederick, MD |
| WellPoint in Frederick, MD |