A pipe joint, the joint comprising: a screw-threaded joint for pipes comprising a first pipe length or pin having at one end a male screw-threaded portion and a second pipe length or box having at one end a female portion having a complementary screw-thread, the portions being adapted to inter-engage along the greater part of the axial length of the threaded portions the screw threads thereof being inclined in the same direction and at an acute angle to the longitudinal axis of the pipe length, the male thread extending to a male stop shoulder adjacent a complementary stop shoulder on the other portion, the complementary stop shoulder comprising a recess in the form of a cone receiver having a rounded apex, the stop shoulder on the pin including a torque shoulder, frictionally engaging a corresponding shoulder in the complementary stop shoulder, a radial surface adjacent a corresponding radial surface on the complementary stop shoulder, a curved sealing surface on the pin sealingly engaging a corresponding curved sealing surface on the complementary stop shoulder of the box, the curved sealing surfaces (16, 24) being so shaped each to lie on the arc of the circumference of a separate circle, the centre of the circle on which the curved surface of the box lies being in the longitudinal direction of the bulk of the box and the centre of the circle on which the curved surface of the pin lies being longitudinally to the opposite side of the point of contact and in the main body of the pin, and that the curvature of the box sealing surface is greater than on the sealing surface on the pin, characterised in that the radius of the circle on which the sealing surface of the pin section is described is from 0.25-0.35"(0.63-0.89cm), and the radius of the circle on which the sealing surface of the box is described is from 0.05-0.07" (0.12-0.18 cm). a screw-threaded joint for pipes comprising a first pipe length or pin having at one end a male screw-threaded portion and a second pipe length or box having at one end a female portion having a complementary screw-thread, the portions being adapted to inter-engage along the greater part of the axial length of the threaded portions the screw threads thereof being inclined in the same direction and at an acute angle to the longitudinal axis of the pipe length, the male thread extending to a male stop shoulder adjacent a complementary stop shoulder on the other portion, the complementary stop shoulder comprising a recess in the form of a cone receiver having a rounded apex, the stop shoulder on the pin including a torque shoulder, frictionally engaging a corresponding shoulder in the complementary stop shoulder, a radial surface adjacent a corresponding radial surface on the complementary stop shoulder, a curved sealing surface on the pin sealingly engaging a corresponding curved sealing surface on the complementary stop shoulder of the box, the curved sealing surfaces (16, 24) being so shaped each to lie on the arc of the circumference of a separate circle, the centre of the circle on which the curved surface of the box lies being in the longitudinal direction of the bulk of the box and the centre of the circle on which the curved surface of the pin lies being longitudinally to the opposite side of the point of contact and in the main body of the pin, and that the curvature of the box sealing surface is greater than on the sealing surface on the pin, characterised in that the radius of the circle on which the sealing surface of the pin section is described is from 0.25-0.35"(0.63-0.89cm), and the radius of the circle on which the sealing surface of the box is described is from 0.05-0.07" (0.12-0.18 cm).