The application of amperometric biosensor- and chemiluminiscence based methods for rapid detection of viable E. coli in water has been investigated. An amplification of the amperometric signal by a factor of 4 was obtained when the cellobiose dehydrogenase (CDH) biosensor was used instead of a plain graphite electrode for detection of b-galactosidase (b-GAL) activity at 22.5°C. A linear correlation was demonstrated for detection time (DT) vs. initial concentrations (logarithmic units) of E. coli lT1 and E. coli in environmental samples, respectively, by use of the CDH biosensor or a chemiluminometric technique. The study has shown that an E. coli concentration ≥ 104 cfu/100 mL in environmental samples was determined by the CDH biosensor within one working day. However, further reduction of the DT can be obtained, e.g. by increasing the signal amplification factor using other biosensors.