Lidar investigations of polar stratospheric aerosols were performed at Ny‐Ålesund, Spitsbergen (79°N, 12°E) between December 1991 and March 1992. Backscatter ratios at wavelengths of 353 and 532 nm and volume depolarization at 532 nm in altitudes ranging from the tropopause up to 30 km are presented. Throughout the whole measurement period a layer of aerosols of volcanic origin was observed. During the period of stable vortex conditions we found averaged peak backscatter ratios of 2.3 at 532 nm at altitudes around 14 km. Before the break‐up of the polar vortex in mid‐March no aerosols were detected at altitudes above 20 km. Observed volume depolarization profiles suggest that the main aerosol layer consisted of spherical particles throughout the whole period of observation. Enhanced values of volume depolarization in the lower part of the aerosol cloud directly above the tropopause are possibly caused by scattering on volcanic ash particles of sub‐micron size. Copyright 1994 by the American Geophysical Union.