Abstract: The invention relates to a heat exchanger, in particular for a motor vehicle, having tubes and if appropriate corrugated fins through which a first, hot medium can flow and which are arranged between collecting boxes, and having at least one side part (1) which is arranged laterally between two collecting boxes, a second medium which flows around the tubes and if appropriate corrugated fins being colder than the first, hot medium during operation, the side part (1) absorbing at least some of the tensile stresses which act at least on the outermost tube as a result of different thermal expansions of the tubes and if appropriate corrugated fins, and the side part (1) having slots (2) and/or openings (4) which change the spring constant of the side part (1) in relation to a side part without slots and/or openings such that, in the event of a different longitudinal expansion of the central tubes relative to the outermost tube which is arranged adjacent to the side part (1), the tensile stress which acts on the ou