A heat exchanger includes a tube bottom made of pressure-resistant and temperature-resistant plastic, and a plurality of tubes which are disposed in side-by-side relationship in the tube bottom and form at least indirectly part of a distribution and/or collecting chamber. The tubes have tube ends which are each provided with a circumferential securing member to inhibit extraction of the tubes from the tube bottom when the tube ends are firmly secured in the tube bottom through a casting process or injection process.