Factors which can influence measurements of the practical range of fast electrons are stated and discussed. These factors can be divided into geometrical parameters, like beam divergence, diameter of the beam and diameter of the detector, and into factors which influence particle energy. It is concluded that the energy-range relations of Katz and Penfold in aluminium and of Markus in water can be used in the energy range from 10 to 30 Mev with a maximum uncertainty of about 2%.