The inner tracking system of the experiment HERA-B

The Inner Tracker of HERA-B, built by the Universities of Heidelberg, Siegen and Zurich consists of 184 chambers with a total of 140000 channels. The detectors are composed of Microstrip Gas Chambers (MSGC) with a pre-amplifying device in the gas volume, the Gas Electron Multiplier (GEM). During the year 2000 we installed and commissioned a total of 136 GEM-MSGC detectors. Preliminary results from the first year of operation are reported.