Abstract: The present invention relates to a nebuliser and method of nebulising a liquid. The nebuliser includes a nebulisation chamber (1) having a well (2) adapted to contain a liquid (3) to be nebulised. An energy source in the form of an ultrasonic transducer (6) has as a curved energy transmission surface (7). This curved energy transmission surface defines a focal point (8) and a focal length (9). The energy source is spaced from the well such that the distance between the focal point and the energy source intrudes into the well not greater than 50% of the focal length. Preferably the well is shaped such that during nebulisation the level of the liquid in the well remains within a predetermined focal length range to thereby provide a substantially constant flowrateut of nebulised liquid. The nebuliser may also include a deflector baffle or fountain diverter (16) which acts to deflect the nebulised liquid fountain rising from the well.