Appropriate methods of assessing the cutting ability of handpiece and rotary cutting instrument combinations are needed for research into the processes involved in dental cutting. They are also required for the development of improved devices and recommendations on operation as well as for equipment specification and standards testing. In reviewing the literature on dental rotary cutting performance testing to evaluate available methods, the factors which may influence clinical cutting behaviour are identified as those related to characteristics of the operator, handpiece, rotary cutting instrument, coolant/lubricant used and workpiece material. Existing industrial cutting theory is of limited help in understanding dental cutting in view of the differences between the control of relevant variables in the two cases. Consideration is given to the ways in which the important variables have (or have not) been controlled in past studies of dental cutting and thus the clinical relevance of available methods evaluated. Serious problems such as the lack of suitable test workpiece materials, as well as deficiencies in current knowledge of operator behaviour, handpiece characteristics and effects of coolant/lubricant application are noted. It is concluded that before improved, clinically relevant tests can be developed, further fundamental research in these areas is essential and that until this is done, further work under arbitrary experimental conditions would be of little value.