Manufacturers of aerosolized medications, approved by the Food and Drug Administration, specify the nebulizer(s) and compressor to be used with their product, in an attempt to achieve efficacy comparable to that obtained in the clinical trials. The need to limit the compressor to that used in the trials has not been investigated in detail. We suggest a technique to determine the equivalency of different compressors such that a chosen nebulizer's performance is not significantly altered. Aerosol particle size (MMD) was measured with a laser; compressor flow and pressure were measured with a mass flow meter and pressure gauge, respectively. For all models of nebulizer, increased flow or driving pressure caused a decrease in aerosol MMD. The flow resistance of nebulizer models varied, and the flow output of compressors decreased as imposed nebulizer resistance increased. However, for any specific compressor-nebulizer combination there is a unique flow and pressure, and the nebulizer generates a given MMD. We demonstrate methods to choose alternate compressors that may be used to drive a nebulizer and yet keep the nebulizer's MMD and performance within predetermined limits. Once an acceptable range of variance in a nebulizer's MMD is defined, alternate compressors may be safely chosen. We recommend that these techniques be used by manufacturers of medications and of compressors to safely determine the acceptability of several rather than a single model compressor to drive a chosen nebulizer. The techniques assure consistency of the nebulizer's clinically demonstrated performance characteristics.