The USEPA National Interim Primary Drinking Water Regulations (NIPDWR) established the maximum contaminant level (MCL) for arsenic at 0.05 mg/L in 1977. Several years ago the USEPA begain to re-examine the arsenic health effects information and has indicated that the MCL could be significantly lower to somewhere in the .0002 to .005 mg/L range. Between 1973-79, DWRD conducted laboratory jar test studies and pilot plant studies to evaluate the effectiveness of a variety of treatment methods to remove arsenic from drinking water. The purpose of the paper is to re-examine the jar test and pilot plant information to determine if these data indicate an ability of conventional treatment methods to achieve arsenic levels below 0.005 mg/L. Radioactive tracers were employed for most of the jar test studies, therefore, the potential existed for determining absolute treatment water levels below 0.005 mg/L. Conventional treatment methods for the paper are classified as lime softening and coagulation filtration.