The altitude distribution of stratospheric gaseous nitric acid was measured on 30 January, 1989 at Esrange (68¿N, 20¿E; Northern Sweden) in a particularly cold stratosphere (lowest temperature 190 K) using a novel rocket-borne ACIMS (Active Chemical Ionization Spectrometry) instrument. Within the coldest layer (18.5--22.6 km) gaseous nitric acid was found to be strongly depleted. Probably this depletion was caused by local nitric acid condensation leading to NAT (Nitric Acid Trihydrate) aerosols, which were still present in the same layer, and/or HNO3-removal from that layer by sedimentation of HNO3-containing aerosols. Threshold temperatures for nitric acid condenstation of about 195--193 K (18.5 km) and 193 K (22.6 km) can be inferred from the present data being roughly consistent with theoretical model predictions. ¿ American Geophysical Union 1990