The air chemistry observatory at the German Antarctic Neumayer Station (NM-II; formerly Georg von Neumayer Station, GvN) is in continuous operation since almost 25 years. It thus provided unique records of atmospheric trace constituents of climatic relevance. The focus of the established observational programme is on characterizing the physical properties and chemical composition of the aerosol, as well as on monitoring the changing trace gas composition of the background atmosphere, especially concerning greenhouse gases. Here a brief outline of the technical concept of the observatory and an excerpt of the most relevant results are presented.