The Cetacean Sound Library at the 'Centro Interdisciplinare di Bioacustica e Ricerche Ambientali' of the University of Pavia (Italy) was created to keep underwater acoustic recordings of cetaceans occurring in the Mediterranean Sea. Recordings were made during research cruises organized by the Centro itself and other Institutions to study the acoustic behaviour, distribution and biology of cetaceans in the Mediterranean Sea. About 137 hours of recordings belonging to sperm whales (which until recently was the target species), striped dolphins, risso's dolphins, bottlenose dolphins, common dolphins, pilot whales, and other sound sources (including man-made noises) are present. Software tools were developed to visualize and analyze stored recordings and to make easier their retrieval and interpretation. As tapes are browsed, a content-database is kept updated to allow access to the cut of interest and to related data such as cruise tracks, bathymetric charts and photographs. Whenever possible sperm whale recordings are linked to a digitized photo-ID (fluke) of the individual. To further develop the sound library, during the last two years a useful partnership with the Italian Navy was initiated, and the Centro is utilised to evaluate biological sounds recorded in ASW (Anti Submarine Warfare) operations.