  We study the systematic inclusion of QED corrections in the evolution of
parton distributions. O(alpha) corrections modify the evolution equation for
parton distributions. They introduce additional parton distributions, like the
photon distribution in the nucleon, and lead to additional mixing effects. We
discuss the modifications for a realistic model of N_f,up up-type flavours and
N_f,down down-type flavours. We have implemented these corrections into a
numerical program and we quantify the size of these effects in a toy model. The
corrections reach the order of 1%.
