Polyamide 6.6 multifilament yarns were converted to crimped fibers by texturing to simulate the properties of natural staple fiber yarns for textile applications. Texturing is carried out by mechanical stresses (turbulences or twisting) under thermal or hydrothermal conditions which affect the fine structure of the fiber. Two polyamide yarns with the same linear density but composed of filaments of different fineness were textured by the False-Twist (thermal) and the Air-jet (hydrothermal) procedures. The influence of texturing and filament fineness on the relaxation behavior of the yarns was studied. (c) 2007 Wiley Periodicals, Inc.