Owing to growing demand for comfortable clothes, elastane filament yarns are being used in fabrics for several garments. In this study, core spun yarns were produced with cotton fibres and PBT/elastane filament yarns (cotton as sheath material, PBT yarn and elastane as core yarns). Twill woven (1/3 Z) fabrics were produced by using core spun yarns (30 tex) and cotton yarns (30 tex) as weft, and 100% cotton yarn (59 tex) as warp yarns. The fabrics consisting of PBT were washed at 100 degrees C for 30 minutes to gain the elasticity. The woven fabrics' weight, thickness, elongation, permanent elongation, dimensional stability, air permeability, thermal conductivity, thermal absorptivity characteristics were tested and statistically evaluated. According to the results, the fabrics containing PBT and elastane filaments had similar elongation and shrinkage values. PBT filament yarns have a great potential to produce lightweight elastic fabrics.