Amniotic fluid volume, Iecithin/sphingomyelin ratio, local phospholipid concentration and total phospholipid per sac were investigated in 53 term pregnancies. A definite influence of amniotic fluid volume on the phospholipid concentration was noted, while no influence on the L/S ratio was observed. Amniotic fluid volume showed a tendency to decrease after the 40th week of gestation. The total quantity of phospholipids per sac showed no significant variation between the 36th and 42nd week of gestation.