The theory of signal detectability was applied to vibrotactile sensitivity in two experiments. The first experiment showed The psychometric function to be satisfactorily linear when a sensitivity index of the d family was plotted against the signal intensity expressed in decibels. The second experiment yielded receiver-operating-characteristic (ROC) curves of a familiar form for the yes-no and rating response methods. Reasonably consistent estimates of sensitivity were obtained in the second experiment from the yes-no. rating, and forced-choice methods. The sensitivity indices examined were d’ and de’, based on Gaussian density functions; A, based on Rayleigh density functions; and the distribution-free indices, P(A) and F(C). For each type of index a tendency was observed for the forced-choice value to be lower than the yes-no and rating values.