The first measurement of the condensation nuclei (CN) profile in the Arctic during winter was made to 31 km on 30 January 1989 from Kiruna Sweden 68¿N). Enhanced levels of CN were observed in the colder regions above 18 km suggesting homogeneous or ion nucleation of CN as observed previously in Antarctica. A CN layer reaching a concentration of about 40 cm-3 was observed between 22.5 and 26 km. Comparisons with data obtained in Antarctica in 1987 and 1988 indicate that this layer is similar to those observed at the same altitude in Antarctica under similar solar illumination conditions. The latter are believed to be of photochemical origin as suggested by measurements before and after stratospheric sunrise. This CN layer may thus serve as a measure of the amount of time an air parcel has spent in the sunlight, an important parameter during the early stages of spring ozone depletion. ¿ American Geophysical Union 1990