Lidar and balloonborne particle counter measurements were performed simultaneously on two days when polar stratospheric clouds were observed in late August 1991 at McMurdo, Antarctica. Both nitric acid trihydrate and ice clouds were observed in the lower stratosphere between 10 and 23 km in different formation stages and with different cooling rate; however in all cases the size distributions were bimodal. Comparison of scattering ratios measured by lidar and calculated from particle size distributions are in good agreement; however, discrepancies were observed when the lower stratosphere was highly perturbed by wave activity. Lee waves generated by air flowing over the Trans Antarctic Mountains induced ice cloud formation at altitudes as high as 20 km. No PSCs were observed after the end of August in 1991. ¿ American Geophysical Union 1992