The invention provides certain 4-keto-phenoxyacetic acids and their oximes of the formula: ##STR1## in which A is selected from oxygen and sulphur, Z is selected from oxygen and the group NOH, and X.sub.1 and X.sub.2 are radicals independently selected from hydrogen, halogen and methyl, with the proviso that the benzene nucleus is never substituted by two halogen atoms in ortho-position with respect of one another, and pharmaceutically acceptable alkaline and amine addition salts thereof.