A simple method is described that makes possible fast evaluation of glass-forming tendency on the basis of relative position of the recrystallization, transformation and melting temperatures. These temperatures are determined by means of DTA. One assumes that the glass-forming tendency is proportional to the thermal stability of glass. The glass-forming tendency is expressed numerically, thus enabling one to compare different kinds of glasses and the influence of various impurities. The validity of the model is experimentally verified on the CdAs2 and As2Te3 systems containing different admixtures.