Glucose transporters (GLUT) catalyse the transport of glucose in many human tissues, including the placenta. On the other hand glucose concentrations can affect both glucose transport activity and level of GLUT mRNA and protein. Up to now very few studies, concerning GLUT in the placenta appeared and studies in vivo in human diabetic pregnancy are lacking. Therefore we investigated placental GLUT 1 and GLUT 3 mRNA in 10 diabetic (5 IDDM, 2 NIDDM, 3 GDM) and 9 non-diabetic women. GLUT 1 mRNA was found significantly correlated with maternal age (> 30 vs < 30 years: p < 0.025), with placental weight (> 575 vs < 575 g: p < 0.05), while GLUT 3 mRNA decreased significantly in late gestation of diabetic women (38-40 vs < 38 weeks: p < 0.025). In addition GLUT 3 was significantly lower in the diabetic than in non-diabetic women in late gestation. These preliminary results deserve to better elucidate feto-maternal carbohydrate metabolism at the placental level in normal as well as diabetic pregnancy.