Polar stratospheric clouds (PSC's) in the 21--24 km altitude range were observed north of Greenland (82--84¿N, 0--25¿W) on January 29, 1988, using an airborne dual-polarization, 0.532-&mgr;m wavelength lidar. Synoptic analyes at the 30-mb level (≈22 km) show local temperatures of 191--193K, which are well above the estimated frost point temperature of 185K and indicate the PSC's were likely of the binary HNO3-H2O (Type I) class. Peak scattering ratios of 1.1--1.2 were measured in the PSC layer, compared to values near 1.05 for the ambient (non-PSC) aerosol over the same altitude range. Profiles of the depolarization ratio distinctly show the PSC layer, but maximum values are 0.06--0.07, only slightly greater than the value (0.04) measured in cloud-free regions and well below the values typically found in cirrus clouds (0.2--0.5). This signature suggests that the Type I PSC's observed during the January flight were composed of small, solid particles having radii on the order of the laser wavelength (≈0.5 &mgr;m). ¿ American Geophysical Union 1988