Technical Abstract: Application of vaccines to commercial caged poultry is being addressed with a plethora of devices, some of which may be associated with inconsistent and non-uniform results. The use of live Mycoplasma gallisepticum (MG) vaccines constitutes a particularly special situation because of the organism's fastidious and fragile nature. Initial studies have been directed at the nozzles and pressures used in applying live MG vaccines. Preliminary results suggest that non-uniform application of MG vaccine is associated with high applicator pressures and nozzles associated with "fine" droplet formation.