Abstract: The invention provides methods and apparatus for the delivery of therapeutic liquids to the respiratory system of a patient. In an exemplary embodiment, the apparatus includes a vibratable non-planar member having tapered apertures which produce droplets wherein about 70% of more of the droplets by weight have a size in the range from about 1 .mu.m to 6 .mu.m. The apparatus may further optionally include a breath sensor which detects the inspiratory flow rate and transmits a signal to vibrate the non-planar member at a frequency corresponding to the inspiratory flow rate. Optionally, the non-planar member may be included in a disposable mouthpiece assembly that is separate from the oscillator assembly. In this manner, the mouthpiece assembly may be discarded after use, while the oscillator assembly may be reused.