The Environmental Protection Agency is amending a variety of testing and monitoring requirements in the Resource Conservation and Recovery Act (RCRA) hazardous and non-hazardous solid waste regulations and for certain Clean Air Act (CAA) regulations that relate to hazardous waste combustors. These amendments allow more flexibility when conducting RCRA-related sampling and analysis by removing from the regulations a requirement to use the methods found in "Test Methods for Evaluating Solid Waste, Physical/Chemical Methods," also known as "SW-846," in conducting various testing and monitoring and by limiting required uses of an SW-846 method to circumstances where the method is the only one capable of measuring the particular property (i.e., the method is used to measure a required method-defined parameter). This action is an important step forward in implementing the use of a performance-based approach, which is part of the Agency's efforts toward Innovating for Better Environmental Results. Additionally, the Agency is making certain other clarifications and technical amendments. These changes should make it easier and more cost effective to comply with the affected regulations, without compromising human health or environmental protection.