The description relates to a process for the production of esters of heparin, wherein from 0.1 to 2 g of a halogenated reagent having the formula R--CH.sub.2--X, where R is a phenyl group which is non-substituted or substituted by a halogen atom or by a nitro group, and X is a halogen atom, preferably chlorine, are reacted with from 2 to 20 g of one of the quaternary ammonium salts of heparin in from 30 to 250 ml of N,N-dimethylformamide and/or N,N-dimethylacetamide. The process in question allows esters of heparin to be obtained at lower cost and within shorter times than the methods known in the art, minimising among other things the use of lachrymatory reagents, such as, for example, benzyl chloride.