Microbiologically Influenced Corrosion (MIC) is not a new type of corrosion, but refers instead to the influence of microbiological activity on known forms of corrosion. Typically MIC promotes pitting corrosion and - to a lesser degree -crevice corrosion. The extent of this promoting effect can vary widely. Raw water with a high content of organic and inorganic matter requires special attention. Typically MIC starts on stainless steels at sites where the corrosion resistance has been lowered by manufacturing methods, e.g, at or around welded joints. The remedial measures are the same as those taken to avoid pitting and crevice corrosion. However, they have to be applied much more rigorously to prevent bacterial action. The most effective remedial action is clearly biocidal water treatment wherever permissible and possible.