The effect of crystallization processes in the xAgI center dot 0.75(100-x)Ag2O center dot 0.25(100-x)P2O5, 50 <= x <= 75, glasses on the ionic conductivity was investigated, using impedance spectroscopy, X-ray diffractometry (XRD) and differential scanning calorimetry (DSC). The crystallization was induced and promoted by thermal processing. It was found out that depending on annealing conditions, the conductivity could be enhanced or lowered. The conductivity enhancement is observed when the glass is annealed near the glass transition temperature T-g for relatively short time. In this case, the XRD patterns do no indicate the presence of crystalline phases. The decrease of conductivity is observed for more pronounced crystallization, detectable by X-ray diffraction. The annealing does not affect the activation energy of ionic conductivity. (c) 2005 Elsevier B.V. All rights reserved.