Lattice dynamic calculations for zeolites and AlPO(4)s were performed at elevated temperatures to evaluate the thermal expansion behavior of these materials. This has led to the interesting prediction in advance of experiments that many zeolites and AlPO(4)s show a negative coefficient of expansion, which means a contraction of their cell volumes on heating. Recent experimental results support these predictions. The success that we had in predicting the expansion behavior of zeolites and AlPO(4)s gives a measure of the reliability of the model and demonstrates the potential of computer simulation techniques.