Abstract: Improved process for preparing 1,2-diacyl-3-glycerylphosphorylcholines, wherein the diacyl groups are, different or the same, a residue of a saturated or unsaturated fatty acid, particularly one of the acyl groups being a residue of a highly unsaturated fatty acid or being a residue of a saturated or unsaturated fatty acid labelled with an isotope, which comprises acylating a glyceryl-phosphorylcholine or monoacyl derivative thereof or the salt thereof with an acylating agent (e.g. 1-acylimidazole or 4-acyl-3-phenyl-1,2,4-oxadiazol-5-one) in the presence of a catalyst (e.g. an alkali salt of a nitrogen-containing 5-membered heterocyclic compound or sodium oxide).