We have examined whether different skin machanoreceptors are activated by different indentation velocities of a tactile probe. Indentations of 300 Β΅m at velocities of 100 and 400 Β΅m/ms were applied at the dorsolateral side of the foot and at the tip of digit III. Compound sensory action potentials (CSAPs) were recorded from the sural and median nerves, respectively. The amplitudes of the tactile CSAPs were <1-2 Β΅V, and less than 15% of the CSAPs evoked by electrical stimulation. The areas of the polyphasic tactile CSAPs were 35-38% smaller at 100 Β΅m/ms than at 400 Β΅m/ms. The maximal sensory nerve conduction velocities (SNCVs) were higher in the median than in the sural nerves. In both nerves, the SNCVs were similar at electrical and 400-Β΅m/ms tactile stimulation but 11-17% lower at 100-Β΅m/ms stimulation. Cocaine hydrochloride was applied iontophoretically at the dorsolateral side of the foot, causing a decrease of 50% of the CSAP evoked by 100 Β΅m/ms but only 14% at 400 Β΅m/ms. These studies suggested that indentation at 400 Β΅m/ms activated mainly deeply placed (Pacini corpuscles) and to some extent superficial mechanoreceptors, whereas the 100-Β΅m/ms indentation activated primarily superficially situated receptors (Meissner corpuscles, and some slowly adapting units).