Rett syndrome (RS) represents a neurodevelopmental disorder of uncertain pathogenesis, featuring an apparent arrest in neural maturation during the perinatal period. Recent findings highlight the intensive ongoing research activities surrounding the neurobiology and neurochemistry of this unique disorder. Abnormalities in multiple neurotransmitter/receptor systems (dopaminergic, glutamatergic, and cholinergic), whether primary or secondary, underscore the pervasive effects of this maturational arrest. The possible role of neurotrophic factors is supported by significantly reduced nerve growth factor levels in cerebrospinal fluid. Similarly, gangliosides and other neuronal markers are perturbed in RS and may represent another critical area of study. The availability of a suitable animal model would accelerate the pace of these important investigations.