Field studies on cetaceans in the Mediterranean Sea have experienced a remarkable development in recent years. Research cruises aboard sailing vessels up to 19 m long were organized by Tethys Research Institute within the seas bordering the Italian peninsula and islands. From 1987 to 1990 recordings of underwater sounds produced by cetaceans in these waters were collected. Recordings were made with traditional reel-to-reel analog tape recorders and high quality underwater transducers. A total of about eight hours of underwater sounds of six odontocete and one mysticete species were recorded. These sounds were subsequently analyzed. The analysis of basic parameters such as duration and frequency range was performed on a Kay Sonagraph DSP 5500 at the Interdisciplinary Center for Bioacoustic Research of the University of Pavia. A cetacean sound library catalogue based on a commercial database was created in order to allow interaction with a PC-based DSP workstation equipped with optical disk for storage of digitized sounds. The aim of this sound library is to provide more information about the acoustic capabilities of cetaceans of the Mediterranean and to allow highly specific access to available data for a variety of potential future applications, such as research and didactical purposes. A current joint research program between Tethys Research Institute and the Center for Bioacoustic Research should provide further opportunities to increase the collected and analyzed data of this library. This research is supported by grants from the Italian Ministero della Marina Mercantile.