The catalytic oxidation, with air, of aqueous solutions of glycerol-derived oxygenates on carbonsupported platinum metals may be controlled to improve yields of valuable fine chemicals. The primary and secondary alcohol functions of glyceric acid, calcium salt, were selectively oxidised by varying the pH and employing a promoter. Under basic conditions, platinum catalyst yielded the tartronate salt (61% yield at 94% conversion, pH 10-11) and slightly higher yields were obtained on bismuth-promoted platinum (83% yield at 90% conversion, pH = 10-11). Hydroxypyruvic acid was obtained on bismuth-promoted platinum under acidic conditions (64% yield at 75% conversion, pH 3-4).