An assembly for an inhalation device comprising a mouthpiece and a heater, said heater comprising a substrate which supports - at least one resistive element portion (514i, ii, iii, iv) applied over a first region of at least one of surface of said substrate, - at least a pair of contacts (513a, b, c, d, e, 513i, ii, iii, iv, v) each connected to the at least one resistive element portion at one end of said contacts and applied over a second region of the said at least one surface of said substrate, - said substrate first region being more proximate a forward or leading edge of said substrate, and said second region being more proximate a rearward or trailing edge thereof, - an amount of an aerosolizable composition deposited on the substrate above said first region on said at least one surface thereof or a surface opposite thereto such that heat generated by said at least one resistive element portion is directly or indirectly conducted to the aerosolizable composition to cause at least some aerosolization thereof, said mouthpiece being provided with a fluid inlet at an upstream, rear end thereof, and a fluid outlet at a downstream, front end thereof, fluid communication means (724A, 724B) being provided internally of said mouthpiece between said inlet and said outlet, said heater being disposed substantially within the mouthpiece in or adjacent said fluid communication means and arranged such that the substrate leading edge more is proximate the mouthpiece fluid outlet and its trailing edge is substantially adjacent the rear end of the mouthpiece such that at least portions of the contacts are both exposed and accessible towards the rear end of the mouthpiece, and such that when fluid is flowing through the fluid communication means and aerozolisation is simultaneously occurring, aerosol generated is entrained in the fluid flowing within said mouthpiece through said fluid communication means, characterised in that the mouthpiece comprises first and second parts (632a, 632b), said mouthpiece first part having a slot which receives the heater which is held in place within the mouthpiece when the second mouthpiece part is attached to said first mouthpiece part, the entire assembly being releasably attachable to a main body part of the inhalation device at the rear end of the mouthpiece, an electrical connection with said exposed accessible contacts being achieved when said mouthpiece rear end is attached to said main body part. - at least one resistive element portion (514i, ii, iii, iv) applied over a first region of at least one of surface of said substrate, - at least a pair of contacts (513a, b, c, d, e, 513i, ii, iii, iv, v) each connected to the at least one resistive element portion at one end of said contacts and applied over a second region of the said at least one surface of said substrate, - said substrate first region being more proximate a forward or leading edge of said substrate, and said second region being more proximate a rearward or trailing edge thereof, - an amount of an aerosolizable composition deposited on the substrate above said first region on said at least one surface thereof or a surface opposite thereto such that heat generated by said at least one resistive element portion is directly or indirectly conducted to the aerosolizable composition to cause at least some aerosolization thereof,