Relationships are presented for converting remote measurements of stratospheric aerosols to surface area and volume densities. Measurements from the Halogen Occultation Experiment (HALOE), the cryogenic limb array etalon spectrometer (CLAES), and the improved limb atmospheric spectrometer (ILAS) were considered. The relationships were derived using an extensive record of in situ aerosol size distribution measurements made in sulfate aerosols and in polar stratospheric clouds (PSCs). Conversions were derived for sulfate aerosols using the appropriate refractive indices, and for PSCs using the refractive indices for either nitric acid trihydrate or liquid ternary H2SO4--H2O--HNO3 aerosols. Coincident measurements from HALOE, CLAES, and in situ particle counters are in generally good agreement at middle latitudes, for surface area and volume. Analysis of CLAES measurements under cold polar conditions suggests that these data should be used with caution. ¿ 1998 American Geophysical Union