Recent amendments to the National Interim Primary Drinking Water Regulations deal with corrosion and require utilities to assess corrosion in their distribution and home plumbing systems. Problems caused by corrosion can be grouped into 3 categories: health, aesthetics and economics. For electro-chemical corrosion reaction to proceed, all components of an electrochemical cell are required - an anode, a cathode, a connection between the anode and cathode and a conducting solution. Corrosivity is affected by many factors, including pH, alkalinity, dissolved oxygen, flowrate, temperature and others. Methods for documenting corrosion range from simple visual inspections to complex scale analysis including weight loss and pitting depth measurements and corrosion probes. Laboratory and pilot tests can be used to define the extent and magnitude of corrosion. Understanding the principles of corrosion is important in avoiding and correcting corrosion problems. Monitoring is important to ensure that the corrosion control program continues to meet its desired objective.