Nearly 300 janitors at Walter Reed National Military Medical Center in Bethesda say they haven't been paid in two weeks.
The Service Employees International Union that represents the janitors says it has filed a complaint against federal contractor, Escab Enterprises.
The union says the company claims it hasn't been paid by the government.
SEIU also says the janitors have been reluctant to strike because of concern for patients at the hospital.
Escab Enterprises hasn't commented on the matter.