Nitrofen is a diphenyl ether herbicide that produces a spectrum of fetal abnormalities in rodents. To characterize the molecular mechanisms of nitrofen-mediated birth defects at the cellular level, we explored its effects on undifferentiated P19 teratocarcinoma cells. Nitrofen induces a time-dependent cell death of P19 cells that is associated with increases in TUNEL-positivity and caspase-3 cleavage suggesting that nitrofen induces P19 cell apoptosis. In addition, the increase in TUNEL-positive cells was inhibited with zVAD-fmk, suggesting that nitrofen induces a caspase-dependent apoptosis. Nitrofen treatment was associated with increased p38 MAP kinase activity, though pretreatment of cells with multiple p38 inhibitors did not affect nitrofen-mediated caspase-3 cleavage, suggesting caspase-3 cleavage is p38-independent. Nitrofen induced a dose-dependent increase in reactive oxygen species (ROS), which was accompanied by a decrease in the ratio of reduced/oxidized glutathione, indicating that nitrofen alters the cellular redox state of these cells. Furthermore, pretreatment of cells with N-acetyl cysteine gave a dose- and time-dependent reduction of caspase-3 cleavage, supporting the observations that caspase-3 cleavage is cell-redox-dependent. Therefore, nitrofen induces P19 cell apoptosis that is cell-redox-dependent and is associated with increases in p38 activity and ROS and may play a role in nitrofen-mediated birth defects.