Detailed height profiles of stratospheric nitric acid mixing ratios have been derived with a baloon borne chemical ionization mass spectrometer by applying several ion molecule reaction schemes, each associated to a specific and selective ion source. These ions (CO-3, Cl-n, CF3O-, and CF3O-H2O) give rise to specific product ions (mainly CO-3HNO3, NO-3HCl, NO-3HF, and CF3O-HNO3) upon reaction with ambient nitric acid molecules. This paper reports on the instrumental details as well as on the results obtained during two balloon flights with the instrument. Within the accuracy of the measurements, the nitric acid height profiles obtained with the three different ion sources are in good agreement with one another as well as with literature data. (Int J Mass Spectrom 181 (1998) 99-111)