EPA guidelines for disposal of solid waste to landfills require that the wastes contain no 'free liquids', where the absence of free liquids is demonstrated by the EPA-prescribed paint filter liquids test (PFLT). The requirement applies to wastewater treatment sludges disposed to landfills. The investigation was conducted to determine whether solids content of sludges could be used in lieu of the PFLT since most treatment plants routinely determine solids content of their sludges. The experiments carried out demonstrated that solids content required to pass the PFLT ranged from 5.5% for waste activated sludge to 15.6% for primary sludges. Agitation such as might be encountered in truck transport of sludge to a landfill did not cause sludges that initially passed the test to fail; however, some sludges that initially passed the test failed after standing for 24 hours.