This work examines the correlation between the H-1-NMR T-2 relaxation constant and the mechanical properties of aged crosslinked polyolefin cable insulation. T-2 experiments on unswollen samples could not differentiate between unaged and highly aged materials; all exhibited H-1 T-2 constants of approximately 0.5 ms. To accentuate the effects of aging, samples were swollen in various solvents. Unaged samples had T-2 values of approximately 15 ms in good solvents. With thermal aging, T-2 values decreased as the ultimate tensile elongation decreased. However, the correlation between T-2 and elongation differed for samples irradiated with high-energy radiation and for materials aged above versus below the crystalline melting temperature. (C) 2003 Wiley Periodicals, Inc.