The conversion of ethanol over H-ZSM-5 was studied as a function of ethanol partial pressure, reaction temp., wt. hourly space velocity, and Si/Al ratio. The results obtained were in qual. agreement with most of those in the literature. Combination with all published results to give a significant regression model was not possible due to the large scatter of the data from various scientific groups. In mechanistic investigations, temp. programmed reaction measurements of ethanol, di-Et ether, and ethene were performed. The formation of ethene from ethanol via direct elimination or from di-Et ether as intermediate could be confirmed. In the conversion of ethanol/water mixts., the product distribution did not change significancy up to a water content of 60 wt%. Then, a pronounced increase of ethene formation and a considerable decrease of the yields of aroms. was obsd. When several reaction mixts. from syngas conversion to ethanol were converted over H-ZSM-5, the coking rate depended on the product distribution in the feed. Product mixts. from processes with higher amts. of compds. having an unfavorable C/H ratio led to rapid deactivation of the zeolite.