Tensile behaviors of the 14 high-manganese steels having stacking fault energy (SFE) range of 13-41 mJ/m(2) using different C, Mn, Cu, Al, and Si contents have been investigated to find a general relationship between SFE and tensile properties in Fe-Mn-C TWIP steels. Cu and Al played similar roles in TWIP steels; however, the effect of Al content was much higher than that of Cu content. Addition of C and Si highly increased the yield strength, but excessive additions led to the premature and early fracture, respectively. The serration flow in tensile curve was not observed when the ratio of Al to C is over about 3.0, which means the critical ratio of Al to C to eliminate the serration flow in high-manganese steels was in existence. Dynamic strain aging decreased the post-necking elongation during tensile test associated with the premature fracture, leading to the decrease in reduction of area (RA) in TWIP steels. It was found that most of the tensile properties such as yield strength, tensile strength, and elongations had no relationship with SFE; however, RA had a relatively higher relationship with SFE, which means RA is a potential indicator to evaluate SFE and twinning behavior in Fe-Mn-C high-manganese steels. Also, twinning stress had a linear relationship with SFE in TWIP steels and Schmid factor of 0.5 was needed to use for polycrystalline metals to evaluate the twinning stress using the models based on the single crystal.