The greater attrition that occurs in machinery components when processing open end cotton yarns than when processing ring spun cotton yarns has led to the opinion that open end cotton yarns are more abrasive, but little published data support this opinion. These experiments investigated the effects of spinning technique on yarn abrasiveness, comparing open end yarns manufactured at different production speeds with equivalent ring spun yarns. The Lawson-Hemphill Constant Testing Transport testing machine measured yarn on metal abrasion by passing a yarn sample over a copper wire and determining the length of yarn required to break the wire. The functions of fiber type, machine type, production speed, and twist level were evaluated. Test results were collated with data obtained from commercial yarns. Rotor spun yarns were less abrasive than ring spun yarns, but systematic differences existed between machines from different manufacturers. The magnitude of the differences in abrasiveness depended on fiber quality. No general correlation between yarn structure and abrasiveness existed. An increase in twist did not lead to an increase in abrasiveness.