Objective To investigate the effects of sterigmatocystin(ST) on the ependymal cells,neurons and endothelial cells of blood vessel of the lateral recess of the fourth ventricle in BALB/c mice in vivo after single oral administration. Methods BALB/c mice were treated intragastrically by gavage with ST 3000??m/kg.The mice were killed 1 hour,2 hours,4 hours,8 hours,16 hours after oral administration respectively for observing ependymal cells,neurons and endothelial cells of blood vessel of the lateral recess with transmission electron microscopy(TEM).Results After oral administration of ST pinocytosis vesicles began to increase in endothelial cells of blood vessel in 1 hour,apocrine of ependymal cells began to increase and myelin sheath degeneration appeared in 2 hours,extensive myelin sheath degeneration and mitochondrion degeneration and incisure and vacuoles in nucleus of neuron were found in 4 and 8 hours.Lipofuscin was found in cytoplasm of neuron 16 hour.Conclusion Oral ST exposure in mice could cause myelin sheath degeneration and damaged changes of neurons.