The glass forming region of the (ZrF4BaF2ThF4)EuF2 system has been studied. EuF2 was found to replace up to about 85% of the BaF2 in a glass with a composition .615 ZrF4, .32BaF2, .07ThF4. The glass transition temperature is seen to increase with the EuF2 concentration. The 4f7→ 4f65d1 transition of the Eu+2 ion in the glass matrix was studied by optical absorption and compared with data taken on crystalline compounds containing Eu+2 in different environments. It is concluded from these results that the Eu+2 ion - and also the Ba+2 ion - is coordinated by 12 fluorides in the glass. © 1979.