Yarns of Giza 85 cotton and rayon and their blends were spun. The rayon fibers in cotton rayon blend ratios are 75 : 25, 50 : 50, 25 : 75, spun on the Schlalhorst Auotocoro 288 OE rotor spinning to pro­duce yarn counts of 2ONe, 30Ne and 40Ne at three twist multipliers; 4.0, 4.4 and 4.8. The effect of blend ratio on yarn properties and yam hairiness has been investigated to define the proper blended yarns. Results indicated that the better yarn quality is obtained at high­er percentage of cotton in the blend. 100% cotton yams produced the strongest lea count strength product and single yarn tenacity. Blended yarn of 25:75 cotton/rayon recorded the lowest yarn strength. Yarn ex­tension at break gradually and steadily increased with increasing the ray­on percent. The increase of fiber length (38 mm for rayon fibers) has no effect on yam unevenness of open-end rotor spinning. The optimum yarn quality has been obtained at 75:25 cotton/rayon blends.