Intrauterine growth restriction (IUGR) is associated with reduced activity of placental amino acid transport systems beta and A. Whether this phenotype is maintained in fetal cells outside the placenta is unknown. In IUGR, cord blood tumor necrosis factor (TNF)-alpha concentrations are raised, potentially influencing amino acid transport in fetal cells. We used fetal T lymphocytes as a model to study systems beta and A amino acid transporters in IUGR compared with normal pregnancy. We also studied the effect of TNF-alpha on amino acid transporter activity. In fetal lymphocytes from IUGR pregnancies, taurine transporter mRNA expression encoding system beta transporter was reduced, but there was no change in system beta activity. No significant differences were observed in system A mRNA expression (encoding SNAT1 and SNAT2) or system A activity between the two groups. After 24 or 48 h TNF-alpha treatment, fetal T lymphocytes from normal pregnancies showed no significant change in system A or system beta activity, although cell viability was compromised. This study represents the first characterization of amino acid transport in a fetal cell outside the placenta in IUGR. We conclude that the reduced amino acid transporter activity found in placenta in IUGR is not a feature of all fetal cells.