Abstract: An autoclave for treating charged materials (6) with vapor under pressure, with a substantially cylindrical inner chamber (2) surrounded by an autoclave casing (1) and with a heating device (8) responsive to a heated heat transfer medium to generate vapor in the inner chamber (2). In order to provide the heating in a way which is favorable structurally and in terms of energy, it is provided that the heating device (8) is arranged within one of the curved side regions of the autoclave casing (1), and consists of at least one flue (10) arranged substantially vertically in the autoclave and a heat exchanger (11) arranged in the lower inflow region of the flue (10) and through which flows a heat transfer medium, so that a convection flow results circulating substantially in the circumferential direction of the casing (1) of the autoclave.