The effect of twist parameters on the structure and properties of OE friction yarn has been investigated. The produced samples were three blended yarns of 100 % cotton, 65% cotton/35 % polyester and 65% cotton/35 % acrylic with ten different twist parameters. Yarn properties such as breaking stress, breaking strain and fiber slip were evaluated. A scheme of fiber classification that characterizes the special shapes and configurations of in OE friction yarns is proposed. Under this scheme, fault fibers are grouped into five different catagories ;hooked, looped, V-shaped, folded and entangled fibers. Data on fiber configurations shows a decrease in the number of fault fibers with increasing twist parameter. Yarn breaking stress shows an increase with increasing twist parameter, but breaking btrain has slightly decreased with increasing twist parameter. Furthermore, the fiber slip related to yarn stability shows rapidly decreasing trend with increasing twist parameter and the twist efficiency in the OEfriction spinner has about 20-30% by change in materials and twist parameters.