1. As an approach to the study of regional or segmental variation in sympathetic activity, skin resistance explorations were conducted on the backs of several hundred subjects under resting, non-sweating conditions. 2. The methods used included the conventional exploration with handheld electrode and two semi-automatic recording methods. 3. The following principles characterize our methods: a) Momentary current flow is read or recorded, in correct spatial relation to the explored area, as the exploring electrode moves over the skin, while a constant voltage is applied. b) Area-to-area variations in resistance upon the general resistance level found in the subject at the time of the exploration, are determined. c) The explorations are conducted under conditions in which resistance is generally high or rising. d) Exploration voltage is adjusted according to general resistance level in such a way that the range of currentvariations is fairly uniform, regardless of the general resistance level. 4. Areas sharply differentiated by low resistance (high current) values were found in all subjects. The patterns of distribution varied from subject to subject. 5. Repeated “sampling” of patterns revealed that the patterns of segmental distribution of the relatively low-resistance areas were highly reproducible and characteristic for each subject, often over periods of many months, and despite large changes in the general resistance level. 6. It is shown that the patterns consist, not of skin areas “fixed” in low resistance, but of areas (segmental levels and sides) in which theprobability of finding low resistance values (high current flow) as compared with the general resistance at any time is high. As compared with all other areas of skin, these areas show much larger and earlier decreases in resistance in transitions from generally high to generally low levels of resistance; the low resistance values are much more persistent in these areas in transitions from generally low to generally high levels of resistance. 7. It is suggested that the factors which determine the area-to-area differences in resistance may be different from those which determine the much larger variations ingeneral resistance level. 8. A segmental origin of at least some of the low-resistance areas was indicated in the frequent presence of apparently dermatomal strips. 9. The relation of ESR patterns, as measured here, to regional variations in excitability of autonomic pathways is briefly discussed.