Seckel syndrome (SS) is a rare, heterogeneous form of primordial dwarfism. The clinical delineation of this disorder has been inconsistent, using even Seckel's original criteria. As a result, probably fewer than one-third of reported cases are truly affected with SS. Among these, there have been only six familial cases, all of whom were born to normal parents, and in only one case has a detailed description of the central nervous system (CNS) anomalies been given. We describe a family in which three of eight children were affected with SS. CNS anomalies seen in our patients included agenesis of the corpus callosum, a dysgenetic cerebral cortex, a large dorsal cerebral cyst, and pachygyria, suggesting an underlying neuronal migration disorder. The parents are first cousins, representing only the second instance of consanguinity, supporting an autosomal recessive mode of inheritance.