Report on cranioplasty by prefabricated plastic implants, reinforced by stainless steel meshes resp. plates or by glass fibre meshes. In frontal cranioplasties the missing orbital roof was reconstructed by the same technique. To avoid infections the nasal sinuses were sealed by a pedicled mucosal flap resp. a free transplanted flap taken from the periosteum of the tibia. All 39 patients operated on this way during the last 6 years are free of complaints and clinical symptoms.