The central nervous system undergoes profound and predictable developmental changes during the first few years of life that provide the structural and functional elements necessary for normal neurological development. The establishment and maturation of white matter pathways is a critical component of the developing nervous system. Diffusion tensor imaging (DTI) offers a noninvasive and quantitative means for the evaluation of white matter changes. DTI has contributed to the evaluation of a number of childhood leukoencephalopathies; it has also been used to follow brain maturation in abnormal states, such as premature birth or early brain injury. Furthermore, it has helped characterize the relation between white matter integrity and cognitive abilities. In the future, DTI is expected to play an increasingly large role in defining developmental abnormalities at an early age and in assessing therapies for pediatric disorders such as leukodystrophies.