The levels of galactose and galactitol in the sera of 6 young adults after ingestion of 0.25 g/kg of galactose alone or with the same quantity of glucose were studied. The results showed that: glucose decreased significantly the galactosemia and galactitolemia observed after ingestion of galactose alone; repeated consumption on 4 consecutive days of galactose alone induced an increase in galactosemia, and more significantly in galactitolemia. The addition of glucose to galactose in the same conditions abolished these effects.