A series of aerosol soundings sensitive to particle sizes in less than about 1 μm was made from McMurdo, Antarctica, beginning in August 1986, while the stratosphere was still cold, and continuing through the spring warming and polar vortex circulation breakdown. The statistical analysis of polar stratospheric cloud (PSC) occurrences at low temperature indicates that there was a combined high probability of sampling such a cloud on at least one of three occasions, but no unusual or definitive features in the profiles were noted that could unquestionably be associated with PSCs. Photographically documented ground observations indicate that there was very likely a PSC or unusual stratospheric aerosol condition present during the first sounding at about 20 km. These aerosol observations impact the present explanations of PSCs and indicate that the possibility of these clouds being made up of low concentrations of relatively large (greater than ~5 μm) particles must be taken seriously. The concentrations would effectively render the PSCs undetectable by the aerosol-sounding equipment employed in this study. It is argued that the fall speed associated with the cloud particles would not measurably change the natural aerosol profile, but that there could be a tendency for some water vapor to be transported to lower altitudes. Because of atmospheric mixing and transport processes, the redistribution of water vapor may not be easily detected. ¿ American Geophysical Union 1988