This chapter 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 is entirely dependent on the quality of information gathered and its respective analysis and interpretation. Continuous or periodic pipeline monitoring activities may be divided into several categories, including: fluids and process monitoring and corrosion monitoring. Cathodic protection (CP) potential surveys are the most common methods used in the industry to monitor the external corrosion of pipelines. Continuous true potential measurement, continuous near line potential gradient measurements, continuous potential measurements by remote electrodes and discontinuous potential measurements on stab plates can be used to map CP potential along the pipeline. When the design of CP for offshore pipelines is highly optimised, the need for monitoring becomes increasingly important.