This study is part of a quality assurance programme evaluating the performances of two connected on-line systems (automatic dosimeter and treatment planning) and verifying the correctness of the applied algorithms and the accuracy of the basic beam data. We compared PDD measured in an automatic water phantom using a p-Si detector with point doses using an ion-chamber, for electron beams from a linac. To record dose distributions of scanned electron beams, the detector measurement time was triggered by the frame scan frequency. Data were automatically transferred to the treatment planning system by an interface. Measured and calculated isodose charts were compared for perpendicular incidence fields. Relative dose values calculated, in axis and off-axis points, were compared with those determined by the ion-chamber in the following situations: perpendicular and oblique incidence, different SSD.