Both a‐c (1000 Hz) and d‐c electrical conductivity of human cortical bone are studied after equilibration at various relative humidities. At the same time weight change measurements are carried out as a function of humidity, so as to determine the moisture content of the bone. Both the electrical properties and weight changes show striking hysteresis when plotted vs. relative humidity. However, when electrical properties are plotted as functions of moisture content the hysteresis is eliminated. The hysteresis effects are attributed to capillary condensation in pores. Measurements were made on samples soaked in Ringer's solution as well as samples washed in distilled water, and also with electric field both parallel and perpendicular to the bone axis. The results of these measurements strongly suggest that the large effect of moisture on conductivity is from ionic salt solutions located in pores and channels.