A section on total coliforms includes a discussion of the most probable number (MPN) test; the membrane filter (MF) test; and the presence–absence (P–A) test. Other indicators discussed include: fecal coliforms and E. coli; fecal streptococci; Clostridium perfringens; Bacteroides and Bifidobacterium; heterotrophic plate count (HPC); and bacteriophages. Finally, standards and criteria for indicators are presented.