The aim of this study was to investigate the activation of the sudomotor component of the sympathetic nervous system caused by chiropractic manipulation. This was determined by measurement of the electrical skin potential changes occurring as a result of activation of sympathetic sudomotor eccrine (exocrine) sweat glands. The electric skin response was recorded from both forelimbs of 20 male chiropractic students who had an asymptomatic first rib fixation and who knew the investigator and technique. The stimuli included auditory shocks (pre- and postadjustment), a set-up for a unilateral first rib adjustment, a sham adjustment and an adjustment to the first rib. The results showed no difference between ipsilateral and contralateral amplitudes or response times. Ipsilateral recordings were observed to be simultaneous with their contralateral counterpart. Furthermore, no statistical difference was found for amplitudes or response times between any two conditions of pre-adjustment auditory shock, set-up, sham adjustment and postadjustment auditory shock recorded from the ipsilateral forelimb. These results suggest that an adjustment applied to a first rib of an unstressed individual familiar with the practitioner and treatment regime results in a bilateral activation of the sympathetic sudomotor response similar to that produced by an auditory shock, set-up or sham adjustment. It was concluded that the first rib adjustment may involve an indirect, generalised activation of short duration on the sudomotor response, probably via all levels of sympathetic control but does not cause any unilateral, direct stimulation of the normally functioning sympathetic nervous system.