Length change and sorption isotherms have been determined for water, ammonia, ethyl chloride, and methane on compacted samples of zeolite NaX. Methane sorption at 0 °C and ethyl chloride sorption at −10°C were accompanied by little or no framework distortion as monitored by length change measurements; sorption of ammonia in the temperature range −50 to −70 °C produced more appreciable distortion; and water sorption at room temperature caused large changes. In each case the framework distortion was correlated with different stages in the sorption process. The sorption isotherms for the ammonia/NaX system indicated the possibility at high uptakes of two-dimensional condensation or multilayer formation. The critical temperature for two-dimensional condensation would be −70 °C.