The distribution of isotopically heavy ozone in the stratosphere has been obtained from an analysis of balloon-based high-resolution thermal emission spectra in the far infrared. The mixing ratio profiles of 16O16O18O and 16O18O16O, retrieved from inversion of several limb sequences of a number of spectral lines in the 39--76 cm-1 region, indicate enhancements over the expected values in the 25- to 37-km altitude range. The ratio of total heavy isotopic ozone 50O3 to normal 48O3 shows enhancements of ~45% at 37 km, decreasing to a minimum of ~13% at ~29 km, and increasing to ~18% at 25 km. The results from this work are compared with Mauersberger's (1987) in situ mass spectrometer measurements. ¿ American Geophysical Union 1987