A balloon borne polarimetric experiment RADIBAL, was launched from Kiruna to observe the properties of polar stratospheric cloud particles, from limb scannings of the radiance and of the polarization of the scattered sunlight. On February 4, 1990 during the CHEOPS 3 campaign, when the stratospheric temperature was about 190 K, a polar stratospheric cloud (PSC) was sampled. At the top of the PSC, an upper thin layer no more than 2 km thick, was shown to be composed of rather large, micron sized particles, as assessed from the forward scattering feature. Difficulties in retrieving they polarization from calculations for spherical particles suggest that thy might be crystalline particles. Below this layer, the PSC consisted very probably of spherical particles. In this part of the cloud, the polarization features indicate that, from the lower to the upper levels, the size distribution of the particles particles⋅narrowed, suggesting a preferential growth process on the smaller class of particles. This preliminary analyzeis, however, is unable to derive a simple model that makes definitively consistent the radiance and the polarization observations, so that the results have to be examined cautiously within the context of prevailing PSC models. ¿American Geophysical Union 1991