This volume contains full proceedings of the Fourth International Conference on Secondary Ion Mass Spectrometry (SIMS-IV), held in the Minoo-Kanko Hotel, Osaka, Japan, from November 13th to 19th, 1983. Coordinated by a local or­ ganizing committee under the auspices of the international organizing com­ mittee, it followed earlier conferences held in MUnster (1977), Stanford (1979), and Budapest (1981). The conference was attended by about 250 participants from 18 countries, and 130 papers including 24 invited ones were presented. Reflecting the rap­ idly expanding activities in the SIMS field, informative papers were pre­ sented containing up-to-date information on SIMS and various related fields. The proceedings focussed upon six main issues: (1) Fundamentals of sput­ tering and secondary ion formation. (2) Recent progress in instrumentation, including submicron SIMS and image processing. (3) SIMS combined with other surface analysis techniques. (4) Outstanding SIMS-related analytical methods such as laser-microprobe SIMS, sputtered neutral mass spectrometry, mass spectrometry of sputtered neutrals by multi-photon resonance ionization, and accelerator-based SIMS. (5) Organic SIMS and FAB which has recently become a rapidly expanding technique in pharmacy, biotechnology, etc. (6) Appl ica­ tions of SIMS to various fields such as metallurgy, geology, and biology, including depth profiling of semiconductors, and analysis of inorganic mate­ rials. As a venue for the exchange of ideas and information concerning all the above issues, the conference proved a great success.