Twist contraction of twisted filament yarns depended on twist factor and processing conditions in twisting. The experimental characterization of the twist contraction of several filament yarns which had different mechanical and physical properties has been carried out under different twist conditions. Spindle-drawn yam, partially oriented yam, draw textured yarn, high tenacity, and trigonal polyester filament yarn were used to characterize the twist contraction effect. The experimentally obtained twist contractions have been correlated with the parameters such as fineness, filament density, packing factor, and modulus. The twist contraction of polyester filament yarns increased with the increase in twist multiplier(T/M) and decreased with the increase in modulus. Also, twist contractions have been correlated with modulus and T/M, rather than shape factor and tenacity of filaments, considered in previous theoretical treatments. The resulting experimental equation can be used to deduce the twist contraction of filament yarns with different characteristics.