Concentrations of gas phase hydrofluoric- and hydrochloric acid have been determined in the upper stratosphere from near-infrared solar spectra recorded in the course of balloon fights from Palestine, Texas, USA (32 ¿N latitude), in October 1978 and in September 1979. The average mixing ratios for HF deduced respectively from these flights are (4.8¿.3)¿10-10 ppv above 30.3km and (6.2¿.5)¿10-10 ppv above 36.8km. This observed difference is ascribed to an increase in the HF concentration out to at least 37km. The HCl mixing ratios deduced from the 1978 flight yield (4.5¿.6)¿10-10 ppv at 21.7km, (7.5¿.7)¿10-10ppv at 27.5 km and (2.1¿.4)¿10-9ppv above 30.5km. Observations in 1979 imply an average HC1 mixing ratio above 36.8km of (2.4¿4.4)¿10-9ppv. Our data do not indicate a measurable temporal trend of the HCl concentration above 30km.