Er-SiAlON glasses were produced by melting appropriate powder mixtures under nitrogen at 1715 degreesC using a cation ratio composition of Er:Si:Al = 3.45:3:2 and with varying nitrogen contents (N= 5 to 22 equivalent %). Chemical durability tests were performed by immersing the specimens into 1M NaOH solution at 75 degreesC. The results were evaluated based on the weight changes of the specimens that were recorded at regular intervals of one week. In this work, the effect of nitrogen content in the glass structure on chemical durability is discussed. Surface features (cavities etc.) on each of the chemical durability tested samples were observed and analysed by a scanning electron microscopy (SEM). Initial results present that Er-SiAlON glasses can be good candidates for applications involving high basicity environments.