We investigated the radiation hardness of GaAs pad detectors irradiated by fast neutrons. The main goal was to determine the degradation of the charge collection efficiency (CCE) of the irradiated detectors and to measure the charge transport properties in terms of the mt-product. Several GaAs pad detectors have been irradiated by fast neutrons (2–37 MeV) with varying fluence (10^12–10^15 n/cm^2). Neutrons were produced at a cyclotron by means of the (p,n) reaction on a thick beryllium target. Alpha spectra and I–V curves were obtained before and after irradiation. Basic parameters for description of charge-carrier transport were determined as dependent on radiation damage. The measurements prove a degradation of the CCE and the disappearance of the rectifying junctions of the detectors as result of radiation damage.