A method for determining aerosol size distributions by single laser-shot single droplet cavity enhanced Raman scattering (CERS) is presented. Droplets are illuminated with the tripled output from a Nd:YAG laser at 355 nm and the CERS fingerprint acquired with a spectrograph and CCD. Droplets with radii in the range 10-50 mum are probed. The extension of this to the determination of a distribution of droplet sizes is illustrated. We suggest that the CERS signature from water could be used to determine droplet size while the observation of Raman scattering from other constituents could be used to identify trace chemical constituents within water droplets. (C) 2002 Elsevier Science B.V. All rights reserved.