Some problems of electron gun design are briefly discussed. The gun is analysed into two separate parts, the triode generator and the final lens, which are considered separately. Preliminary experiments show that cathode tilt in the triode has negligible effect on beam centrality and symmetry. Effects of lateral displacement and tilt of the first anode for various anode/grid spacings are experimentally determined for several types of triode geometry.The effects of displacement, tilt and deformation of the final lens are investigated. Two Appendices are given, the first discussing the experimental technique and the second applying the work to a form of ion-trap electron gun which has found wide use and which has advantages over all other forms of trap.