A radiation hardness study of developed Schottky barrier semi-insulating (SI) GaAs detectors against 5 MeV electrons is described in this paper. The influence of cumulative dose (up to 1000 kGy) and the applied dose rate (20, 40 or 80 kGy/h) on spectrometric and electrical properties of detectors is presented. The spectrometric properties were evaluated from measured 241Am gamma spectra and the electrical properties were obtained measuring the current-voltage characteristics. The cumulative dose has negatively affected all spectrometric properties. The detector CCE (Charge Collection Efficiency) exponentially decreased with dose from initial 74% down to 24% at maximum applied dose of 1000 kGy. The relative energy resolution was increasing from 17% before irradiation up to almost 50% at maximum dose applied. The peak-to-valley ratio firstly increased from 10 to 17 at 24 kGy and then rapidly decreased below 2 at 200 kGy. The electrical properties were obtained from measured current-voltage characteristics of detectors. The breakdown voltage of detectors firstly decreased to 60% of its original value and at few hundred kGy it started to increase exceeding the initial value twice. The reverse current exhibited similar behaviour decreasing up to 200 kGy and then increasing. Concerning obtained results we can determine the limit of sufficient functionality of developed SI GaAs detectors against 5 MeV electrons to be 1000 kGy for 59.5 keV particles. The second investigated parameter of irradiation, the dose rate in chosen ranges, did not greatly alter the spectrometric properties of studied detectors.