Differential SAR interferometry with ERS data has a high potential for surface displacement mapping in the mm to m range. Such displacement information is of interest for the monitoring of phenomena as land subsidence, land slides, earthquakes, volcano swelling, and ice motion. In this contribution the maturity and operational readiness of the SAR interferometric technique are discussed, focusing on the subsidence application. The investigation is based on examples representing displacement velocities between a few mm/year and several m/year. Based on the investigated examples it is concluded that SAR interferometric subsidence mapping reached operational readiness.