The total output from a nebulizer is made up of aqueous droplets containing solute and a significant component of water vapor. The solvent loss is reflected in an increase in the nebulizer solution concentration over time and this has been described mathematically. This theory, originally described by Mercer et al., was modified to describe the solute output from a three-jet Collison nebulizer. The influence of concentration, air flow (air pressure), volume, and temperature on the output parameters were then studied. Inlet air pressures were 10 (4.1), 20 (6.4), and 40 (10.0) psig (L/min), starting concentrations were 0.1, 2, and 5% (w/w) and initial solution volumes were 10 and 20 mL. To study temperature effects, solutions were nebulized at fixed temperatures ranging from 4 to 50 degrees C. This was achieved by water-jacketing the nebulizer flask. Test solutions consisted of mannitol and a fixed concentration of 11.1 micrograms/mL carboxyfluorescein. Nebulization was carried out for up to 30 min using dry, filtered air at ambient temperature. Total output was determined gravimetrically while solute output was determined by fluorimetry (495-nm excitation, 515-nm emission). Solution concentration changes were also monitored over time by fluorimetry. The results show that the solution and solvent output parameters are independent of concentration, volume, and air flow within the ranges studied but that solvent output, in particular, is highly dependent upon temperature.