Nonaqueous unimolar solutions of lithium perchlorate (LiClO4) and lithium trifluoromethanesulfonate or triflate (LiCF3SO3) in γ-butyrolactone (γBL) mixed in (a) 1:1 and (b) 3:2 volume ratios yield mixed salt electrolytes with good conductivity performance with σ25 approaching 10-2 S cm-1. Addition of 10 wt.% of poly(methylmethacrylate) (PMMA) to these liquid electrolytes manifests in producing highly viscous gel electrolytes with η25 in the range of 104-105 cSt and σ25 greater than 10-3 S cm-1. Conductivity and viscosity studies reveal that PMMA plays an insignificant role in controlling the conduction mechanism in gel electrolytes, as they tend to retain the liquid-like behaviour. Also, the dimensional strength bestowed to gels by the polymer stimulates their use in electrochromic windows (ECWs). Inconsequential variation of σ over the operational temperature range of an ECW renders them to be ideal candidates for the same. © 2002 Elsevier Science B.V. All rights reserved.