Abstract: The invention relates to a process for preparing granisetron, or a pharmaceutically acceptable salt thereof, which comprises: a) cyclisation of a compound of formula (I) in an inert solvent and at a temperature between 0–100° C., in the presence of a strong acid, in order to yield the compound of formula (II); b) methylation of the compound of formula (II), with an alkylating agent, in the presence of a base, in an inert solvent and at a temperature between 0° C.–160° C., and with optional formation of a pharmaceutically acceptable salt. The process of the invention yields a granisetron of high purity, preventing impurities due to demethylation, by carrying out the methylation after rather than before cyclisation and with a higher yield.

Abstract: Imidazole derivatives having the formula: ##STR1## Ar is a benzene ring substituted by one or more of the following groups, alone or in combination: halogen, C.sub.1 -C.sub.6 alkyl, C.sub.1 -C.sub.6 alkoxy, trifluoromethyl, and nitro, a process for the preparation thereof and an antiinflammatory, analgesic and antipyretic pharmaceutical composition containing them as active substance are disclosed.