Polar stratospheric clouds (PSC) were observed above Andenes, Norway (69 ¿N, 16 ¿E) with the ALOMAR Rayleigh/Mie/Raman-Lidar during three winters and with an optical particle counter on two occasions. Multiwave-lengths measurements allow the derivation of the parameters of a monomodal particle size distribution and the derivation of volume densitiespaper if the refractive index is known. The particle counter results are used to determine the best refractive index value. The relation of volume density to temperature is compared to thermodynamic models. This confirms that the PSCs observed consist mainly of a ternary solution with low water content. PSC Type I a and I b can be distinguished by backscatter ratio, color ratio and cooling rate. ¿ 1999 American Geophysical Union