The invention concerns the esters of hyaluronic acid in which all or only a portion of the carboxylic groups of the acid are esterfied, and the salts of the partial esters with metals or with pharmacologically acceptable organic bases.The compounds possess interesting and precious bioplastic and pharmaceutical properties and may be used in innumerable fields, including cosmetics, surgery and medicine. The invention also includes pharmaceutical preparations containing, as an active ingredient, one or more hyaluronic acid esters, or a salt thereof as described above, as well as medicaments containing:(1) a pharmacologically active substance or an association of pharmacologically active substances and(2) a carrying vehicle containing a total or partial ester of hyaluronic acid. The invention includes also various uses of the hyaluronic esters or of the above mentioned medicaments, such as in medicine, surgery or cosmetics.The invention also relates to a new procedure for the preparation of polysaccharide esters containing carboxylic groups, such as in particular the above mentioned hyaluronic acid esters.