Altitude profiles of the stratospheric trace gases HNO3 and HCN were simultaneously measured by a balloon-borne mass spectrometer, which was launched on 13 February, 1992 at Kiruna (68 ¿N, 20 ¿E, Northern Sweden). The HCN--profile is nearly constant, around 0.18 ppbv, which is similar to previously measured mid-latitude data. The HNO3--profile measured below 24 km on the descent part of the balloon flight is similar to NOy (≲20 ppbv), and becomes smaller than NOy above 24 km. Probably, the large HNO3, below 24 km, reflect heterogenous HNO3--formation by H2SO4--H2O aerosols from volcano Pinatubo. On ascent HNO3 was substantially decreased around 18 to 24 km, which was possibly due to HNO3--dissolution in H2SO4--H2O aerosols. ¿ American Geophysical Union 1994