The invention concerns novel diarylmethyleneamino-oxyalkanoic acid derivatives which possess useful analgesic properties in warm-blooded animals. In addition certain of the derivatives also possess useful anti-inflammatory properties. Accordingly, the invention embraces oxyalkanoic acids, and simple esters and amides and non-toxic salts thereof, of the general formula: ##STR1## together with pharmaceutical compositions thereof, for use in the treatment of painful inflammatory joint diseases. In addition, the invention provides as a further feature various analogy processes for the manufacture of compounds of formula I. A representative compound of the invention is di-(4-chlorophenyl)methyleneamino-oxyacetic acid which has both analgesic and anti-inflammatory properties.