7-[2-(2-aminothiazol-4-yl)-2-(methylcarbonyloxyimino)acetamido]-3-vinyl-cephem-4-carboxylic acid of formula (I), in the form of a crystalline salt and use thereof, e.g. in the preparation of pure cefdinir. In another aspect this invention relates to the compound of formula (I) in the form of a salt, optionally in crystalline form, wherein the salt is selected from the group consisting of phosphate, hydrogen phosphate, mesylate, tosylate, sulfate, hydrogen sulfate and sulfamate.