Geotechnical instrumentation is of great importance for assessment and evaluation of the safety of dams, and also for delivery of reliable information about their behavior during the construction, operation and post-operation stages, or in the face of any extraordinary event. In the case of tailings sand dams, the construction period coincides largely with their operation, this process sometimes extending over decades. That condition imposes some restrictions on the type of instrumentation and interferences of the dam operation with installation and long-term availability of the instrumentation system. In this article, the Chilean experience with geotechnical instrumentation considered for some high tailings sand dams is presented as an example. In addition, different technologies are discussed.