A portable, handheld breath-actuated inhaler comprises a generally cylindrical body that comprises body portions 1, 3 that receive a canister 2 of pressured fluid such a nicotine to be inhaled in an aerosol by a user, a mouthpiece 7 in the first body portion 1 configured to deliver an amount of the aerosol to the mouth of the user from the canister. A trigger is cocked ready for releasing pressurized fluid from the canister by manually sliding the body portions 1, 3 towards one another. The trigger comprises a compression spring 26 and a cam 33 which engages a pressure sensitive puff lever 28 with a plate 29 that releases the cocked trigger when a user sucks on the mouthpiece and draws in air through air inlet opening 26. Release of the trigger releases spring 26 which slides the body portions apart and also opens a valve in the canister so as to deliver the aerosol to the mouthpiece.