Emission characteristics of single‐crystal LaB6cathodes of 〈100〉, 〈110〉, 〈111〉, 〈210〉, 〈310〉, and 〈321〉 orientations, with large tip radius (100 μm), were investigated. In cathodes of small tip radius (less than 10 μm) emission from the conical face is dominant, as it has the small area of the top surface. Cathodes of large tip radius have a large emission area at the top surface, which includes various crystal faces, according to the orientation and the cone angle. It has become clear that it is important to use as the tip axis the orientation having rotational symmetry and a crystal face of low work function at the cathode top to get good beam uniformity. In this respect the 〈100〉 cathode was found to be superior to cathodes of other orientations. Emission characteristics of the 〈100〉 cathode during long‐term operation were investigated. A flat (100) face was formed at the top due to LaB6material consumption, and emission characteristics reflecting this tip shape were measured.