This paper reports on research studies conducted by the Library of Congress (LC) on the factors affecting the service life of compact discs.A natural aging pilot study was initiated in 1996 as part of a plan to formulate a strategy to preserve the Library's growing collection of music on CD by periodic monitoring of the condition of the discs. After 10 years of testing the original sample set of 125 discs at selected intervals the study was expanded to include 1050 more discs to achieve a more representative sampling of the Library's collection to date. Sampling, testing, storage, and data analysis for both studies are discussed.Two accelerated aging studies were conducted to explore the mechanisms of optical disc degradation. The first study used a single stress condition to evaluate the effect of security labels on CDs. The second study used multiple elevated stress conditions to observe the differences in disc failure rates in a heterogeneous population, and to evaluate the effect of laser engraving a property stamp on the disc. The initial Block Error Rate (BLER) and its rate of change was used as the indicator of service life, with the value of 220 per second signaling the end-of-life. Observations of physical degradation on both a macro and micro scale and their effect on disc life are included.Aluminum oxidation is widely considered to be the primary cause of disc deterioration. Results of the accelerated aging studies suggest that several factors are at work. Initial work to correlate life expectancy with chemical composition is described.