The maximum speed at which voluntary vocal and digital responses can be initiated was investigated in 15 male and 15 female neurologically normal adults using simple reaction time (RT) methodology. All subjects were pretrained to respond as quickly as possible to stimulus onset following a computer-controlled preparatory interval. Voluntary minimal RTs for phonation initiation were studied as a function of (1) stimulus type (auditory and somesthetic), (2) prephonatory vocal-fold position (abducted and adducted), and (3) subject's lung volume (75%, 50%, and 25% VC). The average minimal vocal RT across subjects was 195 msec, and the fastest recorded vocal RT was 120 msec. Although vocal responses to an auditory stimulus were somewhat shorter than to a somesthetic stimulus, neither these differences nor the RTs between sexes were statistically significant except that females had shorter vocal RTs from an abducted prephonatory vocal-fold position. Shorter vocal RTs were obtained when phonation was initiated at midlung volume than at the lung volume extremes, and for both sexes the average digital RTs were significantly shorter than vocal RTs.