The invention is based on a multi-chamber flat tube (V1-V17) having at least two chambers (1, 2) for holding the flow of a fluid, produced by deforming a sheet-metal strip, in particular produced in a bending and/or folding and/or crimping process, in which a closed profile is formed by: opposite wide walls (4, 6) which are connected to one another by means of opposite narrow walls (5, 7) which form in each case one deformed region, with the wide and narrow walls forming outer sides of the profile, with a first wide wall (4) being formed by an inner section of the sheet-metal strip which is situated between side sections of the sheet-metal strip, and with a second wide wall (6) being formed by side sections, which are arranged to the sides of the inner section, of the sheet-metal strip, with the first and second wide walls (4, 6) being connected by means of a web (3) which separates at least two chambers and which forms an inner side of the profile and which is formed by an edge section (3A, 3B) of at least one of the side sections, with only one of the side sections having an edge section (3A, 3B) which runs continuously, in particular from an inner side, of the second wide wall (6) to, in particular an inner side, of the first wide wall (4) and is connected there in a cohesive manner, in particular by means of soldering, at a contact point (8), with the continuous edge section having at least two deformed sections (3B.1, 3B.2, 3B.3, 3B.4, 3B.5) and at least one of the deformed sections forming a contact surface (9) for an edge section (3A) of the other side section. To improve a multi-chamber flat tube of said type, the invention provides the following possible measures, if appropriate in combination. In a first variant, that deformed section of the continuously running edge section (3B) which forms the contact surface (9) may run obliquely or at right angles with respect to the second wide wall (6), and at least one further deformed section of the continuously running edge section (3B) may run obliquely or at right angles with respect to that deformed section of the continuously running edge section (3B) which forms the contact surface (9). In a second variant, that deformed section of the continuously running edge section (3B) which forms the contact surface (9) may be one of a plurality of deformed sections which are arranged in a v-shape, s-shape, u-shape or o-shape or so as to be wound or folded. In a third variant, it is possible for the edge section (3A) of the other side section not to have a deformed section and to be part, in particular of the first or second region, of the second wide wall (6). In a fourth alternative, the edge section (3A) of the other side section may have only deformed sections (V11-V14) which run at right angles or parallel to the second wide wall, in particular only deformed sections which are arranged in an i-shape or l-shape. The invention also encompasses a multi-chamber flat tube in which at least one of the chambers (1, 2) is formed by a plurality of walls, in particular two walls, and the web (3) has at least two of said walls, and at least one edge section (3A) of the side sections is fixed to the web (3). The invention also encompasses a corresponding heat exchanger and a corresponding use of the heat exchanger.