Objective: To evaluate the effects of different frequencies of auricular (ear-to-ear) sine-wave transcutaneous electrical nerve stimulation (TENS), administered at subliminal intensity, on trigeminal nerve sensitivity.Design: In a double-blind protocol, healthy volunteer subjects were administered one of three different frequencies of active TENS (5, 100, or 2,000 Hz) or placebo TENS (no current was passed) for 30 min.Setting: Department of Psychology, City University of New York.Subjects: 72 healthy undergraduate volunteers with no preexisting pain problems (16 men and 56 women), from the Department of Psychology, City University of New York.Outcome measure: Pretreatment to posttreatment changes were measured in sensation threshold for a 250-Hz electrical stimulus applied transcutaneously to an area 1 cm anterior to the tragus of the ear (mandibular division of the trigeminal nerve).Results: Analysis of variance indicated no group differences in baseline trigeminal sensation threshold, but there were significant group differences in pretreatment to posttreatment changes in sensation threshold (p < 0.001). A postiori analysis showed significant increases in trigeminal sensation threshold after active TENS as compared to placebo TENS (p < 0.05), with 5− and 100-Hz TENS producing significantly greater hypesthesia than 2,000-Hz TENS (p < 0.05).Conclusions: Sine-wave auricular TENS produces frequency-dependent trigeminal hypesthesia that is not a placebo effect.