Cerebral palsy is a common affliction in childhood. In some cases, the spasticity that often occurs can be treated with dorsal rhizotomies. Classically, these procedures have not been performed in children in whom there are known specific congenital brain malformations. The authors report on two patients with holoprosencephaly and unilateral schizencephaly who underwent dorsal rhizotomy to treat their spasticity. The results were good. The long-term benefits during a mean follow-up period of 3.5 years included the transition from using a walker to quad canes for ambulation. Additionally, the outcomes in these two children appeared comparable to those found in other children with spastic diplegia undergoing dorsal rhizotomy at the authors' institution. Dorsal rhizotomy may prove useful for treating spasticity in children with known congenital brain deformities.