Plasma endothelin 1 concentrations were determined in infants with meconium stained amniotic fluid. Plasma endothelin 1 concentration in the study group (5.23 pg/ml) was statistically higher than that in the control group (1.12 pg/ml). Cord blood pH and base excess values were significantly lower in infants with meconium stained amniotic fluid when compared with the control group. There was no correlation between endothelin 1 concentrations and pH or base excess values. Results suggest that meconium passage is not a physiological event, even if meconium stained infants appear to be clinically healthy.