Book excerpt: The subject of the workshop was the Gallium Arsenide and related compounds devices for Physics research and applications. The topics were the GaAs detectors for the experimental apparatus, the characterisation of the materials and the detectors, the GaAs electronics and optoelectronics, the radiation hardness and the x-ray detectors for x-ray imaging in medical applications. The purpose of the workshop was to discuss the status of the art of these fields in view of the construction of devices for the stringent demands imposed by the future Physics experiments and the applications in term of speed and radiation hardness.