The invention relates to a new process for the preparation of 17,18-dehydro-apovincaminol-trimethoxy-benzoate of the formula (I) ##STR1## and acid addition salts thereof. According to the invention compound of the formula (I) is prepared starting from 17,18-dehydrovincamine of the formula (IIa) ##STR2## and/or 17,18-dehydro-epivincamine of formula (IIb) ##STR3## by reducing with a complex metal hydride, acylating the new hydroxy-vincaminol derivative obtained selectively with 3,4,5-trimethoxy-benzoic acid or a derivative thereof capable of acylation, optionally in the presence of a catalyst and/or an acid binding agent, and treating the corresponding acylated hydroxylderivative obtained with formic acid, in the presence of an acid chloride, and, if desired, converting the compound of formula (I) obtained into an acid addition salt thereof.