Electric transport measurements of thickness-dependent electronic and ionic conductivity of epitaxial Ag2S films are used to split both kinds of conductivity into bulk and surface components. The established considerable electronic and ionic surface conductances demonstrate unambiguously the co-existance of electronic and ionic space charge regions in the vicinity of silver sulfide free surface oriented along the zone axes [(1) over bar0 (1) over bar]. The parameters of both space charge layers - surface potential, thickness of the space charge region and concentration of the surface compensating charges, are calculated. It is estimated that for intrinsic silver sulfide, the effective surface potential of ((1) over bar0 (1) over bar) Ag2S surface is negative, its value being about -610 mV at 400 K. (c) 2005 Elsevier B.V. All rights reserved.