New process for the production of the pentahydrate of ceftazidime of formula ##STR1## characterized in that the ester group of the compound of formula ##STR2## or an acid addition salt thereof, is cleaved by the sole use of aqueous hydrochloric acid, and the resulting ceftazidime is either crystallized directly from the reaction mixture as the pentahydrate by adding a base, or first of all the dihydrochloride of the ceftazidime is isolated by adding acetone and/or ethanol or another anti-solvent which is miscible with water, and this is converted into the pentahydrate by known methods.