Amniotic fluid concentrations of Zn and Cu were measured in human pregnancy of 12-44 wk gestation. Although mean values for both metals were relatively flat throughout pregnancy, there appears to be a relative increase in Cu levels between 26-33 wk gestation and increasing levels of Zn after 34 wk. Correlations with fetal age or fetal-maternal disease were not apparent in specimens from this heterogenous population.