A method for testing intensity and duration of the effect of local anaesthetics is presented. The assessment of effectiveness is based on the subjective perception threshold after painful electrical tooth pulp stimuli. With respect to its practical applicability the method is tested in a clinical study using three commercial local anaesthetics. The results prove the possibility of giving reproducible and quantitative statements concerning the time course and intensity of anaesthesia. Using this method, only a restricted number of subjects is necessary for estimating the differences in the basic features of different local anaesthetics.