Bi-doped calcium aluminosilicate glass materials (CAS), with the concentration of Bi 3+ ions 0.5, 1.0 and 3.0 mol %, were prepared by conventional melting. The basic properties and thermal behavior were studied by X-ray diffraction (XRD), He-pycnometry, X_Ray Fluorescence (XRF) and differential thermal analysis (DTA). XRD analysis showed the presence of crystalline gehlenite traces in samples with the highest Bi content. Crystallization of gehlenite in all prepared samples and crystallization of Bi 2 O 3 in case of samples with 1 and 3 mol.% Bi 3+ content was observed by a combination of DTA and XRD analysis. The increasing ability to crystallize was correlated with the increasing Bi content in the samples.