Major craniofacial operations for the treatment of congenital malformations are now firmly established following Tessier's (1967) pioneering work and the unavoidable risks which they carry, are fairly generally agreed. It is, therefore, timely to consider the factors which are important in the preoperative assessment of patients for surgery, the indications for recommending it and the complications which may be encountered. This review is based on 46 cases operated upon by the craniofacial team at the Hospital for Sick Children over a 6-year period. It represents about 500 hours of operating time. The series consists of 31 cases of hypertelorism, of which 23 were corrected transcranially and 8 extracranially, and 15 cases of craniosynostosis, of which 9 were corrected transcranially (Apert 5, Crouzon 4) and 6 extracranially (Apert 2, Crouzon 4). © 1979.