First test-beam results with a prototype of the LHCb vertex detector

The current design of the LHCb vertex detector (VELO: VErtex LOcator) is described. The use of the VELO detector in the second level trigger and the radiation environment at the LHC influence the choice adopted. A first prototype of the detector has been tested on test beams at CERN, and first preliminary results are presented in this contribution.