This paper records the results of a series of measurements carried out on waveguides and components of the type suitable for long-distance transmission.The description opens with a short discussion of methods of measurement, their applications and shortcomings. The reasons for choosing a pulse-testing method are explained, and the special equipment is briefly described. The measurement difficulties are discussed in detail, and some apparently conflicting results are explained. The problem of mode identification is tackled in a number of ways, and some experimental results are recorded. A number of components are studied and particular attention is paid to the feeds. Bends and corners are investigated in some detail, and it is claimed that, with suitably designed waveguides, these need not be a major design problem. In fact, using the techniques described, very satisfactory bends and corners can be made with relative ease.Some abridged results of numerous measurements carried out on plain metallic pipes under various conditions are recorded, and it is concluded that such waveguides are unsuitable for long-distance transmission. Performance figures of corrugated and helical Waveguides are quoted, and it is concluded that electrically satisfactory waveguides can be designed.