The McNamara - O'Hara Service Contract Act (SCA) applies to every contract entered into the United States or the District of Columbia, the principal purpose of which is to furnish services to the United States through the use of service employees. The SCA requires contractors and subcontractors performing services on covered federal or District of Columbia contracts in excess of $2,500 to pay service employees in various classes no less than the monetary wage rates and to furnish fringe benefits found prevailing in the locality, or the rates (including prospective increases) contained in a predecessor contractor's collective bargaining agreement. Safety and health standards also apply to such contracts.

The compensation requirements of the SCA are enforced by the Employment Standards Administration's Wage and Hour Division (WHD) within the U.S. Department of Labor (DOL). The SCA safety and health requirements are enforced by the Occupational Safety and Health Administration (OSHA) within DOL.