Abstract: A heater, especially an auxiliary motor vehicle heater, with a burner in a combustion chamber (2) which is surrounded by a generally pot-shaped, die cast heat exchanger (4) which has inner and outer parts (5, 6) and between which an intermediate space (11, 12) is formed through which a heat exchange medium flows, the combustion gases emerging from the combustion chamber (2) being discharged via a exhaust outlet connection (23). To increase the heat transfer efficiency and to minimize the size of the heater, on the outside of the open end of the heat exchanger inner part (5) a ring (15) is provided which projects, spaced apart from the outer peripheral wall (7) of the inner part, toward the bottoms (8, 10) of the heat exchanger parts. The intermediate space (11, 12) continues from between the peripheral walls (7, 9) of the inner and outer heat exchanger parts to between the ring (15) and the peripheral wall (7) of the inner part (5).