Abstract. The metabolism of guanosine in human erythrocytes has been studied in two different experimental systems – direct incubation and dialysis incubation – the latter allowing continuous addition and removal of substances. Intra‐ and extracellular purine compounds were analyzed using high‐performance liquid chromatography (HPLC). At 37°C, a normal pH (7.4) and a favorably high concentration of inorganic phosphate, guanine nucleotides were synthesized at a substance rate of about 0.17 mmol · h‐1 (calculated per liter erythrocytes) when guanosine was kept at a concentration of 25 μmol · I‐1. At a higher guanosine concentration the rate of synthesis increased only moderately. Erythrocytes loaded with guanylates lost these nucleotides at a rate of 0.023 mmol · h‐1 at a normal phosphate concentration and somewhat slowlier at a higher phosphate concentration. The metabolism kept the guanylates in an equilibrium that was similar to the equilibrium between the adenylates.