Microbially influenced corrosion of carbon steel in anaerobic environment is difficult to monitor with electrochemical techniques because of heterogeneous surface conditions and electrochemically active corrosion products. Weight loss measurement, LPR, EIS, hydrogen permeation, and a refined ER technique have been evaluated including field tests in soil and marine sediment. The conclusions are that EIS can detect combined biofilm and corrosion product film formation, but corrosion rate is overestimated. The ER technique seems to give a correct and sensitive corrosion rate measurement within minutes. Hydrogen permeation measurements can indirectly identify sulphide.