Two cotton / viscose yarns, one in which a thin strand of long staple viscose fibers spirally wrapped the yam surface and the other in which the viscose fibers remained scattered in the body of the yam, were produced and their properties compared with a 100% cotton yarn. An attempt was made to determine viscose fiber compositions that give maximum strength in the two kinds of cotton / viscose yarns. The experimental yams were used as filling yams in a plain weave fabric and the fabrics compared for strength, abrasion resistance, and stiffness properties. As expected, the two cotton / viscose yarns reached optimum strength at a twist factor considerably lower than that required for the 100% cotton yam. Also, at the optimum twist factor, both the cotton / viscose yarns were stronger than the corresponding 100% cotton yam. Optimum yarn strength was associated with a 10% viscose composition in both yams. The strength of conventional cotton / viscose yam (draw frame mixed) showed greater sensitivity to viscose fiber composition, while that of wrapped yarn showed less sensitivity. In the fabric stage, the wrapped yam accounted for better tensile strength and abrasion resistance and increased flexural rigidity.