To develope the medium count open-end spun yarn, process conditions ranged from opening and picking to open-end spining were examined. Being considered the factors as combing roller r.p.m., cotton grade, twist multiplier, the physical properties of the product spun in open end spinning frames were tested. From this research, the results are as follows. It is considered that twist is not a critical factor affecting single yarn strength because of the twist structure of open-end yarn. The decrease of single yarn strength as increase of yarn count makes the spinning of high count open-end yarn difficult, but it was found that medium count yarn can be spun by optimum process conditions of carding room.