AbstractA method for the enzymatic synthesis of hexoses‐3‐14C and hexoses‐4‐14C is presented. The procedure is based on the synthesis of 3‐phosphoglyceric acid‐1‐14C (3PGA) by the action of the ribulose diphosphate carboxylase in the presence of ribulose‐1,5 diphosphate and14CO2, followed by the reversal of the glycolytic reactions leading from glucose to 3PGA. For the synthesis of hexoses‐3‐14C, dihydroxyacetonephosphate‐1‐14C and cold glyceraldehyde‐3‐P are condensed by the aldolase reaction, while for the synthesis of hexoses‐4‐14C cold dihydroxyacetonephosphate is condensed with glyceraldehyde‐3‐P‐1‐14C. The problems and the