Diffusion tensor imaging (DTI) was performed on 15 fresh spontaneously or therapeutically aborted normal fetuses and five term infants at different gestational ages. Regional cortical fractional anisotropy (FA) values were observed to increase with gestational age (GA) from 15 to 28 weeks, followed by a decrease through 36 weeks. The early increase in the cortical FA value, which has never been reported before, is consistent with neuronal migration from the germinal matrix. A statistically significant inverse correlation between GA and the FA values in the germinal matrix was observed (r = -0.81, P = 0.004). In addition, there was a significant difference in the FA values in the right and left frontal cortices (P = 0.007, sign test), suggesting cortical lateralization during the early stage of development. Our studies suggest that the DTI-estimated anisotropy could be useful in following neuronal migration, cortical maturation, and associated changes in the germinal matrix during early brain development.