The experience acquired during 10 years treatment of 33 children having undergone a large craniectomy with an average follow-up time of 5.3 years is presented. Different methods of primary and delayed closure of the skull defect are documented and discussed. Whenever possible the deep frozen conserved skull flap was reimplanted. The problem of skull flap resorption and insufficient spontaneous ossification and the alternative of a heterologous cranioplasty with methylmethacrylate (MMA) in cases of insufficient reossification is considered. The decision to use MMA as a secondary skull defect graft should be delayed at least one year after craniectomy, since a spontaneous reossification of the defect is possible until adolescence.