A heat exchanger, such as a condenser or gas cooler, having a collecting tube which has a wall and which can be produced by deformation of a single metal strip, which collecting tube has, in its base, at least one row of openings in which heat exchanger tubes, each of which has two narrow and two wide sides, are fastened at their ends. The collecting tube can have at least two chambers, which adjoin one another approximately at a central longitudinal axis, and also a reinforcement, which is formed by the longitudinal edge strips of the metal strip.