Myelin transcription factor 1 (MyT1) is a zinc-dependent, DNA-binding protein, and is known to be expressed in early progenitors of oligodendrocytes. We examined the immunoreactivity of MyT1 in developing human brains and brains with periventricular leukomalacia (PVL) to understand the relationship between the expression of MyT1 and myelination in PVL brains. MyT1-positive glial cells were first detected at 19 gestational weeks (GWs) and then gradually increased until 26-29 GWs in the control group. Then they decreased and became very rare at 1 year of age. The expression of MyT1 immunoreactivity shifted from the nucleus to the cytoplasm of the glial cells in the developmental time course. In the chronic stage of PVL, MyT1-positive cells were significantly increased around necrotic foci and some of the regions were coincident with increasing MBP and PLP immunoreactivity. These results may reflect myelin repair on dysmyelination around PVL areas. Therefore, MyT1 may play an important role in the myelin repair in PVL regions.