An experimental investigation of the low-energy electron immersion objective in the range 20-70V has revealed new features of interest in the study of beam distribution and characteristics. For example, the beam current shows a saturation effect over a considerable portion of the modulation range; further, beam-trimming electrodes absorb maximum and minimum fractions of the cathode current for particular values of the ratio α of anode to modulator voltage.Using an arbitrary convention of measuring beam width, there appears to be a minimum beam radius at about 40V for all beam angles, and an indication of a second minimum at higher energies and smaller beam angles. These and the marked change in distribution with voltage and with α are attributed to space charge repulsion effects.The simple space charge theory breaks down for the lowest energies; the limit for production of an axial beam lying at about 20 volts. The trajectories in the presence of space charge indicate that even for the lowest emission densities, the `crossover' may be considerably displaced.