Abstract: An X-ray tube including a cylindrical vacuum envelope at whose frontal or end surfaces are disposed the high voltage leads for the anode and the cathode. The vacuum envelope comprises a cylindrical metal member with at least one end surface face thereof being closed in a vacuum tight manner by means of an annular ceramic member with one of the high voltage leads, and possibly further leads, passing through the central opening of the annular member in a vacuum tight manner, so that the insulating path between the associated high voltage lead and the metal cylindrical member extends in a predominantly radial direction. Preferably the outer surface of the annular ceramic member forms an angle with a plane perpendicular to the longitudinal axis of the X-ray tube which angle is equal to or less than 45.degree., and more preferably equal to or less than 30.degree..