A study has been made of different aspects of the catalytic action and possible use of VPI-5 crystalline aluminophosphates, including those modified with Si and Mn, in the isomerization of o- and m-xylenes, the disproportionation of toluene, the alkylation of toluene by methanol, and the dehydration of n-butanol and isopropanol at atmospheric pressure. It has been established that, in conversions of hydrocarbons, VPI-5 synthesized with the use of di-n-propylamine is inactive, while Mn-VPI-5 possessing (according to IR spectroscopy of sorbed pyridine) greater H+-acidity, is more active than Si-VPI-5. In the dehydration of alcohols, the catalysts can be placed in the following order of activity: VPI-5 < Si-VPI-5 < Mn-VPI-5. The influence of the reaction medium on the structure and catalytic properties of aluminophosphate molecular sieves in the reactions investigated is discussed. Catalysts based on VPI-5 and M-VPI-5 crystallites are compared with faujasite and pentasil systems.