Abstract: The downhole portion of the system of the present invention provides entirely downhole methods and apparatus for the monitoring and control of wells. The components of the system are modular. There are sensor and control valve components located in each of the multi-zone production intervals or lateral well completions. The production zones are isolated by production packers equipped with feed-through conductors for communication to upper system components. There are a monitor and control module containing a programmable microprocessor controller and a power supply module which are located at the uppermost end of the system. The system provides for removing, decommissioning and/or replacement of the power module or the monitor and control module without decompleting the well.The surface portion of the system may be operated from the wellhead or by remote control.