Chalcohalide glasses in the CdSe-Agl-As2Se3 system were synthesised and characterised for the first time. The glass-forming range for (CdSe)(x)(Agl)(0.5-x/2)(As2Se3)(0.5-x/2) compositions was found to be limited to x <= 0.20 without any significant change in the glass transition temperature but with two sub-regions with decreased (x <= 0.05) and increased (x >= 0.10) crystallisation ability. The glasses belong to ionic conductors and their conductivity decreases drastically with increasing x accompanied by simultaneous increase of the activation energy. The observed changes in the ionic transport properties are caused by two independent mechanisms: (i) an exchange reaction, CdSe + 2AgI reversible arrow Cdl(2) + Ag2Se, taking place in the glass-forming melt, and (ii) blocking of Ag+ preferential conduction pathways by cadmium. (c) 2010 Elsevier B.V. All rights reserved.