A composite pipe made of plastic for air conditioning and ventilation technology - with a smooth inner pipe, - with a corrugated outer pipe, which has -- corrugation crests (3, 4) each formed by two flanks (7, 8) and an outer annular surface connecting them to each other, and -- in each case between directly adjacent corrugation crests (3, 4) has corrugation troughs which are bounded to the inner pipe by corrugation feet connecting the corrugation crests (3, 4) to one another, wherein the corrugation feet are welded to the inner pipe along the circumference of the composite pipe, and wherein the corrugation crests (3, 4) have a profile height h and a pitch t from the center of one corrugation foot to the center of the immediately adjacent corrugation foot - with opposing large side wall portions (15, 15'), of which one large side wall portion is formed to be curved outwardly, - with small side wall portions (13, 13') connecting the large side wall portions (15, 15') to one another, which are opposing one another and are formed in a part-circle shape with an outwardly curved radius of curvature R1, - with a small axis passing through the large side wall portions (15, 15'), wherein the small side wall portions (13, 13') are arranged in mirror symmetry with respect to the small axis, and - with a large axis passing through the small side wall portions (13, 13'), characterized in that - both large side wall portions (15, 15') are formed to be curved outwardly and are arranged in mirror symmetry with respect to the large axis and are each formed symmetrically with respect to the small axis, and - that the small side wall portions (13, 13') and the large side wall portions (15, 15') are each connected to one another by means of a transition portion (16, 16'), wherein the transition portions (16, 16') are each formed from a rectilinear partial portion (17, 17') opening out of the respective small side wall portion and a part-circular portion (18, 18') connecting the respective rectilinear partial portion (17, 17') to the associated large side wall portion (15, 15'), and - that for the profile height h and the pitch t of the corrugation crests (3, 4) the following applies: h <= t. - with a smooth inner pipe, - with a corrugated outer pipe, which has -- corrugation crests (3, 4) each formed by two flanks (7, 8) and an outer annular surface connecting them to each other, and -- in each case between directly adjacent corrugation crests (3, 4) has corrugation troughs which are bounded to the inner pipe by corrugation feet connecting the corrugation crests (3, 4) to one another, wherein the corrugation feet are welded to the inner pipe along the circumference of the composite pipe, and wherein the corrugation crests (3, 4) have a profile height h and a pitch t from the center of one corrugation foot to the center of the immediately adjacent corrugation foot -- corrugation crests (3, 4) each formed by two flanks (7, 8) and an outer annular surface connecting them to each other, and -- in each case between directly adjacent corrugation crests (3, 4) has corrugation troughs which are bounded to the inner pipe by corrugation feet connecting the corrugation crests (3, 4) to one another, wherein the corrugation feet are welded to the inner pipe along the circumference of the composite pipe, and wherein the corrugation crests (3, 4) have a profile height h and a pitch t from the center of one corrugation foot to the center of the immediately adjacent corrugation foot - with opposing large side wall portions (15, 15'), of which one large side wall portion is formed to be curved outwardly, - with small side wall portions (13, 13') connecting the large side wall portions (15, 15') to one another, which are opposing one another and are formed in a part-circle shape with an outwardly curved radius of curvature R1, - with a small axis passing through the large side wall portions (15, 15'), wherein the small side wall portions (13, 13') are arranged in mirror symmetry with respect to the small axis, and - with a large axis passing through the small side wall portions (13, 13'), - both large side wall portions (15, 15') are formed to be curved outwardly and are arranged in mirror symmetry with respect to the large axis and are each formed symmetrically with respect to the small axis, and - that the small side wall portions (13, 13') and the large side wall portions (15, 15') are each connected to one another by means of a transition portion (16, 16'), wherein the transition portions (16, 16') are each formed from a rectilinear partial portion (17, 17') opening out of the respective small side wall portion and a part-circular portion (18, 18') connecting the respective rectilinear partial portion (17, 17') to the associated large side wall portion (15, 15'), and - that for the profile height h and the pitch t of the corrugation crests (3, 4) the following applies: h <= t.