The spray characteristics of an effervescent atomizer operating in the MPa injection pressure range are reported. This work will serve as a preliminary study in the effort to apply effervescent atomization to the fuel injection process in Diesel engines. Spray mean drop size (D-32) and drop size distribution width (indicated by the Rosin-Rammler exponent N) are reported as functions of injection pressure, atomizing gas-to-liquid-ratio by mass (GLR) exit orifice diameter, aerator tube geometry, and radial distance from the spray centerline. Spray cone angle is also reported as a function of injection pressure and GLR. D-32 is seen to increase slightly with an increase in GLR and to decrease with an increase in exit orifice diameter. The aerator tube geometry is seen to have some influence on D-32. Finally, the spray cone is found to widen with an increase in GLR and injection pressure.