CORROSION TESTING of pipelines is done for several reasons. One is to evaluate the pipeline condition to determine whether or not it is safe to operate. If repairs are needed, testing is performed to determine if repair is feasible or if replacement is needed. Testing is performed to track the pipe condition so that repair or replacement can be budgeted. Another reason for testing pipes is to evaluate the effectiveness of corrosion control measures, such as inhibitors for internal pipe surfaces or cathodic protection for internal or external surfaces. This chapter provides information on test techniques that can be applied to metallic pipes above ground or buried in an aqueous environment. Prior to discussing test techniques, the chapter will discuss briefly the materials and corrosion issues affecting pipelines. This chapter is by no means a detailed text on corrosion of pipelines, and the reader is encouraged to consult the references for further detail.