This article continues a discussion of the revision of the USEPA drinking water regulations begun in the December 1984 issue of OpFlow. There are many contaminants for which Maximum Contaminant Levels (MCLs) may be changed. This is due to experience gained in implementing the regulations since 1977, new scientific and health data, and advances in analytical capability. In addition, new contaminants probably will be added and others dropped. Specific contaminant considerations which are dealt with in this article include: coliforms, turbidity, giardia lamblia, viruses, legionella, standard plate count, and inorganic chemicals.