Advanced well and reservoir management techniques have been developed to optimize the recovery of modern, complex completions. Permanent sensors deployed in the wellbore and along the tubing, in the surface production network, and in the facilities provide a rich data flow to support these techniques. Sensor evolution from mechanical devices through electronic systems to optical technologies has increased the data flow supporting production operations to unprecedented levels. Sensors in today's wells measure pressure, temperature, oil, gas and water flow rates, resistivity, and seismic signals. © 2008 Society of Exploration Geophysicists.