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-threaded portion, the portions (15,25) 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, the stop shoulder on the pin further comprising a radial surface adjacent a corresponding radial surface on the complementary stop shoulder of the box, a convex curved sealing surface of the radial surface on the pin sealingly engaging a corresponding convex curved sealing surface on the corresponding radial surface on the complementary stop shoulder, characterised in that the curved sealing surfaces (14,24) are each so shaped to lie on an arc of a long axis of a separate ellipse, wherein the long axis of the ellipse described by the curved sealing surface on the box section is from 0.1420-0.1650" (0.3607-0.4191cm) in length, and wherein the long axis of the ellipse described by the curved sealing surface on the pin section is from 0.1250-0.1550" (0.3175-0.3937cm) in length. 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-threaded portion, the portions (15,25) 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, the stop shoulder on the pin further comprising a radial surface adjacent a corresponding radial surface on the complementary stop shoulder of the box, a convex curved sealing surface of the radial surface on the pin sealingly engaging a corresponding convex curved sealing surface on the corresponding radial surface on the complementary stop shoulder, characterised in that the curved sealing surfaces (14,24) are each so shaped to lie on an arc of a long axis of a separate ellipse, wherein the long axis of the ellipse described by the curved sealing surface on the box section is from 0.1420-0.1650" (0.3607-0.4191cm) in length, and wherein the long axis of the ellipse described by the curved sealing surface on the pin section is from 0.1250-0.1550" (0.3175-0.3937cm) in length.