The Library of Congress is the largest library in the world. It has an enormous collection that includes over 29 million books and printed materials; 2.7 million audio and motion picture recordings; 12 million photographs; 4.8 million maps; 4 million musical compositions; 58 million manuscripts; and numerous museum-type objects. The collection is composed of highly complex organic materials, most of which are natural and man-made polymers, that degrade over time. To develop effective strategies for long-term preservation of the collection, fast, preferably non-invasive, and specific mass spectrometric analyses are needed to identify (1) compounds that are either formed via or that contribute to degradation processes; (2) organic compounds that are present inherently as part of collection objects; (3) the �fingerprint� composition of housing materials that meet Library archival specifications; and (4) contaminants in the Library environment that can negatively impact the collection. The relatively recent advent of Direct Analysis in Real Time (DART^TM) mass spectrometry is providing a new and efficient method for accomplishing all the above, including non-invasive MS analyses of some types of collection objects. This presentation will include experimental details of how to obtain reproducible results while showing examples of how the Library is using DART^TM-MS to identify products from accelerated and natural aging of paper-based materials; to identify organic media inherently present in objects and used in past and current conservation treatments; to develop mass spectral libraries of polymeric collection and housing materials; and to analyze organic contaminants in the Library environment.