Atmospheric electrical parameters have been investigated in the Carlsbad Caverns. 222Rn concentrations of the order of 65 pCi/l in the Caverns during the summer maximum results in a high rate of ion-pair production estimated to be about 2300¿106 ion pairs m-3 s-1. This leads to ion densities of about a thousand times that of the free atmosphere. Electrical conductivity values of approximately 150¿10-14 (&OHgr; m)-1 were measured which exceed those of outdoor air by a factor of the order of 100. Mobilities for positive and negative small-ion populations in the Caverns during the summer, appear to be less than mobilities reported for small ions in the free atmosphere. The lower mobility of the cave ions relative to outdoor fair-weather conditions is attributed to a combination of high humidity and low condensation nuclei concentration in the cave enviroment. An electric field of approximately 1 V m-1 was measured near the floor of a tunnel in the Caverns. This suggests the presence of net negative space charge equivalent to about 0.4¿108 ion m-3.