Following the biannual meetings in MUnster (1977) and Stanford (1979) the Third International Conference on Secondary Ion Mass Spectroscopy was held in Budapest from August 31 to September 5, 1981. The Conference was attended by about 250 participants. The success of the 1981 Conference in Budapest was especially due to the excellent preparation and organization by the Local Organizing Committee. We would also like to acknowledge the generous hospitality and cooperation of the Hungarian Academy of Sciences. Japan was chosen to be the location for the next conference in 1983. SIMS conferences are devoted to two main issues: improving the application of SIMS in different and especially new fields, and understanding the ion formation process. Needless to say, there is a very strong interaction be­ tween these two issues. The major reason for the rapid increase in SIMS activities in the last few years is the fact that SIMS is a powerful tool for bulk, thin-film, and surface analysis. Today it is extensively and successfully applied in such different fields as depth profiling and imaging of semiconductor devices, in isotope analysis of minerals, in imaging biological tissues, in the study of catalysts and catalytic reactions, in oxide-layer analysis on metals in drug detection, and in the analysis of body fluids.