The tool wear in interrupted cutting has been investigated from various points of view. In this study, for cases accompanied with the torsional vibration of themain spindle system, hitherto undiscussed, some aspects of the flank wear are examined. From two-dimensional interrupted turning experiments, using the apparatus and the technique newly developed for this study, the following results were obtained. (1) The flank wear is directly influenced by the interrupted cutting variables : frequency of interruption n0, interrupted cutting ratio β, amplitude of cutting force Fc, and amplitude of rotational speed vibration dΩ. But the influence of cutting edge temperature θ was not observedin these experiments. (2) Under comparatively low wear condition such as examined in this study, the increment of the volumetric wear is approximately proportional to the amplitude of the rotational speed vibration and the other variables above mentioned. From these experimental results, a description of the volumetricwear by the above interrupted cutting variables is attempted, and a wear equation can be identified with sufficient accuracy.