Since March 1992 the total column abundances of several tropospheric and stratospheric trace gases have been monitored year-round from Ny Alesund, Spitsbergen. The short-lived tropospheric trace gases C 2 H 2 , C 2 H 6 , and CO exhibit large seasonal variations with a summer minimum, caused by reaction with OH. CH 2 O shows a second maximum during the summer, caused by its formation by methane oxidation. For the long-lived gases HF, N 2 O and CH 4 the seasonal cycle is less pronounced and is forced mainly by wintertime stratospheric diabatic descent, which starts in early November and reaches a maximum in March. The chemical repartitioning of HCl into ClONO 2 starts in November and they are converted into their active counterparts between December and March.