This colloquium on Atmospheric Trace Constituents held in Mainz on July 1, 1981, was a joint one-day meeting of all scientific working groups of the SFB-73. The purpose of this meeting was to provide a fairly intensive and comprehensive review of the SFB-73 research work during the last two years and to discuss the state and the problems as well as possible future developments of the various projects. According to the scientific program of the SFB, the meeting consisted of two separate sessions devoted to actual research problems of trace gases (session I) as well as aerosol particles (session II) in the atmospheric environment. As in previous years, each of the 14 partial projects presented its efforts at least by one research contribution. In nearly twenty papers and discussions, methods, results and the present state of art as well as particularly numerous open questions in the experimental and theoretical studies could be explained. The range of topics considered can be gauged from the contents of this publication. The proceedings contain almost all papers presented at the colloquium. These papers have been issued as quickly as possible. Most of the authors devoted considerable efforts to keep within tight time and space deadlines. It is a pleasure to acknowledge these efforts here. A few number of papers, however, could only be re· ceived with a considerable time extension and this unfortunately caused an editorial delay of several months.