In December 2001 and 2002 in situ aerosol measurements were made from balloon-borne platforms within polar stratospheric clouds (PSC) consisting of supercooled ternary solutions, nitric acid trihydrate and ice. Particle size (radius >0.15 m) and number concentrations were measured with two optical particle counters. One of these included an ~80 cm inlet heated to >244 K to obtain measurements, within PSCs, of the size distribution of the stratospheric particles upon which the PSC particles condensed. These measurements are compared to models that calculate the evaporation of PSC particles. The modeled evaporation for supercooled ternary solutions is in good agreement with the measurements. For nitric acid trihydrate it is uncertain what happens to the particle as it is brought to temperatures >50 K above its equilibrium temperature at stratospheric partial pressures. Here the modeled evaporation show too low evaporation compared to the measurements.