Pyrolysis-gas chromatography was used as an analytical method to evaluate the extent of chemical changes that occur in aged yarns and to demonstrate any correlation between measured physical properties and pyrolysis products. Nylon 6,6 yarn samples (2.5-3.0 milligrams) that were control-degraded as a function of humidity, temperature, and time were pyrolized at 500°C and chromatographed on a Graphpac AT-1000 column. The peak heights of pyrolysis products unique to the degraded material were correlated with measured tensile strength loss (-5 to -75 percent) of the yarns. Linear relationships were found for several of the products, one of which was identified as caprolactam. Significant changes in the pyrograms were observed in nylon with tensile strength losses of 5 percent or less. (Abstractor's note: This is a method for predicting long term stability of polymer materials.) -- AATA