Accurate and consistent pain threshold measurements for the tooth pulp [human] were achieved with careful preparation of a moisture-proof appliance and the use of a high-quality constant-current stimulator. Using an extant dental filling as the cathode, the usual problems associated with the control of the stimulation area and locus and, consequently, current density can be overcome. Repeated measurements showing less than .+-. 5% variation over many months can be routinely achieved on the same individual. The technique showed a high degree of sensitivity to common analgesic agents and is potentially useful for the investigation of variations in pain threshold over extended periods of time.