Multiwavelength lidar observations of Polar Stratospheric Clouds (PSCs) are performed by the AWI at Ny-Alesund, Spitsbergen (78.9°N, 11.9°E) since winter 1991/92. PSCs are the most important contribution to the polar stratospheric aerosol content, since volcanic aerosols from Mt. Pinatubo eruption decreased to background values. Lidar measurements of the backscatter ratio at three wavelengths and the depolarisation allow the characterisation of PSCs with respect to their abundance, shape (spherical or aspherical) and optical characteristics. Model calculations and above all back trajectory analysis of the temperature history of the PSCs permit conclusions about their chemical composition. A comparison of first results of the actual winter 1995/96 with previous winter periods will be given. The relevance of the occurance of the PSCs for the chemistry of stratospheric ozone and trace gases will be discussed.