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An investigation is reported in which the lifts of the roller necks of the upper of each of the sets of drafting rollers in a drawframe were measured. Data expressed in the ft*equency domain showed that roller errors could be clearly seen at the fundamental frequencies of the various rollers when the error and the measurements related to the same set of rollers. Some harmonics were also visible. When errors were in one set of rollers and the measurements were made down the fibre-flow line, the sharpness of the peaks was greatly reduced by drafting waves in the fibres flowing through the system. It was deduced that drafting waves dispersed the singular frequencies produced.An absolute encoder was used on a bottom roller to average out asynchronous signal components and randonj errors. The averaged data demonstrated the roller shape under dynamic conditions even when the error was small. It was possible to use a ratio technique to produce a virtual encoder for the top roller. At start-up, the viscoelastic properties of the rubber covering, the distance apart of the rollers, and the error levels changed as the rubber warmed up. The djniamic shape of the roller could be determined, and the result was repeatable.