High-density micron-sized aerosols from liquid surfaces were generated using an ultrasonic (frequency = 1056 kHz) nebulization technique in the absence and presence of a number of surfactants. The surfactants included cationic surfactants, cetylpyridinium chloride and dodecylpyridinium chloride, and anionic surfactants, sodium dodecylbenzenesulfonate and sodium benzenesulfonate. The nebulization process generated aerosols of a narrow size distribution with a number mean diameter of about 3.4 mu m, which is close to the theoretical value suggested by the Lang Equation. The aerosol droplets are enriched in surfactant as a consequence of the large interfacial area. The enrichment factor varied for different surfactants, depending on their surface activity. The extent of enrichment can be related to the rate of mass transfer of surfactant to the liquid surface. Surface concentrations of between 15 and 30% of the equilibrium value are observed, indicating turbulent mass transfer is the rate limiting step.