The performance of five different compressors (CR60), Porta-Neb, Pulmo-Aide, TurboBoy and Freeway Freedom) was studied in combination with the widely recommended PARI LC PLUS nebuliser for the aerosolisation of a marketed tobramycin solution (TOBI). The droplet size distribution of the generated aerosol was measured with laser diffraction technique at stationary inspiratory flow rates through the nebuliser cup of 20, 30 and 40l N/min. The different compressors showed a distinct difference in droplet size distribution of the aerosol and nebulisation time till dry running. The finest droplets with a volume (equals mass) median diameter (mmd) of 1.84 microm (which was the same at all flow rates), as well as the narrowest size distribution were obtained with a CR60. The Freeway Freedom generated the largest droplets: mmd ranged between 2.63 and 3.72 microm depending on the inspiratory flow rate. The aerosol produced with this compressor also had the widest size distribution. The differences between the compressors could be explained with differences in the jet flow. A higher jet flow resulted in finer droplets, less dependence on the inspiratory flow rate and a shorter time till dry running. Thus, to obtain the required fineness of the aerosol for peripheral airway deposition of the tobramycin, independent of the inspiratory flow rate, the use of the CR60 compressor is preferred over the use of Porta-Neb, Pulmo-Aide, TurboBoy and Freeway Freedom (in order of decreasing preference). Finally, it was found that careful cleaning with warm water and liquid soap of the nebuliser cup is essential to obtain adequate performance of the LC PLUS.