A new instrument for simultaneously measuring aerosol diameter from 0.4--10 &mgr;m and the refractive index between 1.30--1.60 has recently been flown on the NASA ER-2 aircraft during a stratospheric measurement campaign. Average stratospheric refractive indices varied from 1.40 to 1.42 over a latitude range from 70¿ S to 50¿ N and from 1.34 to 1.46 over a vertical range from 4--20 km. The measured stratospheric refractive indices do not agree well with theoretical predictions and vertical profiles suggest the presence of non-spherical or absorbing particles in the altitude range of 7--9 km. ¿ American Geophysical Union 1996