Objective:To measure fetal lung volume by echo‐planar magnetic resonance imaging (MRI).Methods:Twenty singleton pregnancies were scanned on one occasion each using echo‐planar imaging, a form of MRI. Cases of fetal growth restriction and macrosomia were excluded from the study.Results:Lung volumes increased with gestational age from 21 mL at 23 weeks' gestation to a maximum of 94 mL at term. The relation between lung volume and gestational age was exponential. The ratio of lung volume to total fetal volume decreased with gestational age.Conclusion:The use of echo‐planar imaging allows estimation of normal fetal growth; it has clear applications for the diagnosis of lung hypoplasia and potential use for the study of lung maturity.(Obstet Gynecol 1994;83:951‐4)