The objective of this research was to investigate the time-dependent behaviors of yarns, which have significant bearings upon the properties of stretch fabrics made from them. In this study, 100% wool, wool-lycra (W-L) (97 : 3), and polyester-wool-lycra (P-W-L) (52 : 45 : 3) blended yarns were considered. These yarns were subjected to the tensile fatigue failure, stress relaxation, and creep experiments. The findings showed that of these three yarns, P-W-L blend exhibited maximum fatigue lifetime, stress retention, and creep recovery, the pure wool yarn followed suitalbeit to a lesser extent, whereas the W-L blend made it least. The investigation suggests that wool alone with lycra as a core component is not sufficient to impart the expected properties upon stretch fabrics, rather a blend of polyester and wool with lycra as in the former would definitely make a worthwhile product. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 2123-2126, 2011