Forms of discharge tests are described and compared. The use of the Arman and Starr discharge bridge with cathode-ray-tube display is shown to be practicable for bushing testing up to 600 kV. Spurious discharge effects and the precautions necessary to eliminate them are discussed. Consideration is given to calibration methods and to the errors to be expected with various practical circuits. The problem of establishing safe discharge limits for bushings is considered on the basis of a large number of test results and on service experience.