Corrosion monitoring may be defined as the systematic and continual direct or indirect measurement of system corrosivity. Its objective is to assist in the understanding of the corrosion process and/or to obtain information for use in controlling corrosion and reviewing mitigation actions. This chapter (Fig. 5.1) outlines the requirements, methods and information required to carry out internal as well as external corrosion monitoring of pipelines. It includes a section on data management as successful pipeline corrosion management (PCM) is entirely dependent on the quality of information gathered and its respective analysis and interpretation.