The CMS Electromagnetic Calorimeter

The CMS electromagnetic calorimeter is a very challenging detector which aims at providing high precision calorimetry in the Large Hadron Collider (LHC) environment. It consists of about 75,000 PbWO /sub 4/crystals that have to operate reliably for at least 10 years, in a high radiation environment. The readout electronics must sustain high data rates. In the last year new radiation hard readout electronics and a new cooling system were adopted and successfully tested. A large effort was also devoted to test the first modules performance in an electron beam, to validate the monitoring system and the calibration strategy. With more than one-third of the barrel modules produced, the calorimeter is well into its construction phase. An overview of the calorimeter design and of its construction status will be given, as well as the predicted performance at the LHC.