Using instruments to gather information on the performance of an embankment dam is vital. The safety and proper functioning of a dam must be assessed continuously- during construction, during first filling of the reservoir, and during the service life of the dam. Many types of instrumentation systems are used for embankment dams. Systems monitor water pressure, seepage, internal movement, surface movement, vibration, and other significant parameters. The various instrumentation systems used by the Bureau of Reclamation are described in this manual, which is intended for designers, engineers, instrument readers, dam operators, and dam safety personnel. The history, purpose, and current usage of each type of system is discussed. Each system is described; its advantages and disadvantages are analyzed; and its installation, monitoring, and data handling procedures are outlined.