Abstract: A method of manufacturing a heat exchanger comprises temporarily suporting a number of tubes in a first mould using a plurality of removable tube plates. The first mould is then filled with a molten, low melting alloy. After the alloy has set, the assembly is removed from the first mould and the tube plates are disintegrated by solvent or chemical action. The assembly of tubes supported by the set alloy is then inserted into a second mould and plastic material is injected into the mould to form a thin shell around the tubes and alloy and may also form header tanks of the heat exchanger. Finally, the whole assembly is removed from the second mould and the alloy is melted out to leave the completed heat exchanger. The method is also applicable to the manufacture of other hollow articles having a complex internal configuration.