  The Laser-wire will be an essential diagnostic tool at the International
Linear Collider. It uses a finely focussed laser beam to measure the transverse
profile of electron bunches by detecting the Compton-scattered photons (or
degraded electrons) downstream of where the laser beam intersects the electron
beam. Such a system has been installed at the PETRA storage ring at DESY, which
uses a piezo-driven mirror to scan the laser-light across the electron beam.
Lat- est results of experimental data taking are presented and compared to
detailed simulations using the Geant4 based program BDSIM.
