Research on the torsional behavior of singles yarns focused on the experimental evaluation of a theory developed for two different cases of yarn torsion. The research compared predicitions of torque-twist relationships based on this theory with data collected on woolen spun carpet yarns processed at varying twist levels. Typical theoretical predictions of the relative contributions of fiber tension, bending, and torsion to yarn torque, and of variations in both fiber tensile strain distribution in yarn and yarn axial and lateral dimensions that occur during twisting were also calculated. The research showed that yarn jammed progressively from the inside to the outside during twisting at a constant length. The outer fibers were initially unstrained, and, according to Postle's theory, these fibers were assumed to carry a real tensile strain. The presence of a large helix angle indicated the potential for tension generated torque, which explained why other theories of yarn torque yielded prediction significantly higher than experimental results. The new theory yielded satisfactory predictions of observed torque behavior in woolen carpet yarns, given the limitations associated with these materials. 5 refs.