Background/purpose: Measurement of skin surface and stratum corneum (SC) hydration during clinical and/or experimental trials needs devices with acceptable reproducibility and sensitivity under conditions ranging from increased and normal to low hydration. A previous study comparing Corneometer® instruments (European group for Efficacy Measurement of Cosmetics and Other products - EEMCO) used for measurement of electrical capacitance of skin indicated a major difference among Corneometer® instruments. The aim of this study was to assess threee inter-instrumental similar Corneometer® instruments (two pieces of CM820 and one CM810) in normal skin. We named them CM-A(CM820), CM-B(CM820), and CM-C(CM810). Methods: The hydration state of SC measured as electrical capacitance of six body sites were measured in 53 subjects with three Corneometer® instruments. Result: We found that the Corneometer® instruments displayed close capacitance levels. When one Corneometer® was plotted against another the regression line indicated a good correlation among instruments albeit a major and random disagreement could appear in individual sites as an exception. Conclusion: Three Corneometer® instruments evaluated in this study gave close measurements and correlated well. Nevertheless, pretest validation of instruments should be undertaken in multicenter studies where capacitance data are compared or pooled, and concordance among instruments should be documented prior to study. © Blackwell Munksgaard, 2005.