Total coliform bacteria (TC), fecal coliform bacteria (FC), and Escherichiacoli are the most common bacterial indicators of sanitary significance in water microbiology. In Norway, surface waters are the main source of drinking water. Approximately 1800 water works supply a population of 4 million. The current Norwegian standard for FC and TC analyses are quite similar to the membrane filtration and multiple tube fermentation methods given by the International Standards Organization (ISO). Both methods use fermentationof lactose to indicate the presence of target bacteria. However, preliminary studies with enzyme-based methods have been carried out during the last three years in Norway. The method examined is based on defined substrate technology (Colilert-18/Quantitray(TM)). As an introduction to a quantitative comparative study, the confirmation of TC, FC, and E. coli by lactose and indole tests was compared with the activity of the specific enzymes B-D-galactosidase (GAD) and B-D-glucuronidase (GUD). Includes 14 references, tables.