Abstract: A double-wall tube for a heat exchanger and method for producing same, the tube being formed by two tubular walls (1, 2) mounted one inside the other with a very small clearance (3)and then made to have a tight fit therebetween, the outer surface of the inner wall (2) and the inner surface of the outer wall (1) being interconnected by a thin layer of brazing metal in regions (4) which are discontinuous both in the circumferential direction and in the longitudinal direction of the tube. The brazed regions (4) represent 5 to 15% of the confronting surfaces of the inner wall (2) and outer wall (1) of the tube. The invention is in particular applicable to steam generators of fast neutron nuclear reactors.