In 1986, Congress amended the Safe Drinking Water Act requiring USEPA to regulate 83 contaminants within 3 years according to a specified scheduled time, and 25 more contaminants every three years starting in 1990. The majority of the 83 contaminants to be regulated will be organic compounds with only about 15 being inorganics and radionuclides. When EPA sets a regulation (a maximum contaminant level) for a contaminant, it must also specify the 'best available technology' (BAT) that can be used to remove the contaminant. Because the regulations apply to community water systems, the technologies selected are ones that are commonly used to treat community size water systems. Thus, EPA R&D program has focused its efforts on evaluating primarily community applied technologies such as conventional coagulation-filtration, lime softening, ion exchange, adsorption, and membrane process. When BAT is identified for a specific contaminant, frequently the BAT will be listed with its limitations because the process is often not effective under all water quality conditions. These same limitations would also apply to POU/POE treatment. The paper discusses EPA's regulations on inorganic contaminants, the best available technologies cited by EPA, and the limitations of these processes. Using arsenic as an example, the impact of the contaminant chemistry and water quality on removals is presented.