The reduction procedures which are applied to raw data from the Galileo and Ulysses Dust Detectors are described in order to obtain physical parameters (mass and velocity) for the recorded dust impacts. Both detectors are impact ionization detectors which measure the charge released from an impact onto a solid target. From the rise times of the signals, impact speeds from 2 to 70 km s -1 can be derived with an accuracy of about a factor 2. Electronic impact charges are measured from 10 -14 to 10 -8 C, which refer to a speed dependent mass range (e.g. 4 × 10 -15-4 × 10 -9 g at 20 km s -1 impact speed). Larger particles are recorded with saturated signals. Data processing performed both on board the spacecraft and on the ground is described. The processing allows dust impacts to be identified and separated from noise events. Supplementary information, such as impact time and sensor pointing at the time of impact, is also provided.