Many patients with a clinical diagnosis of "nonsyndromic" coronal craniosynostosis have been found to be heterozygous for the fibroblast growth factor receptor 3 (FGFR3) mutation Pro250Arg. The phenotype associated with this mutation is variable and lacks highly distinctive features, so it is difficult to diagnose on clinical examination alone. The authors present a retrospective study of 76 patients with isolated coronal synostosis who were operated on in a single dedicated craniofacial unit over 25 years. The authors investigated whether any single factor, including the presence of a FGFR3 Pro250Arg mutation, predisposed to an increased transcranial reoperation rate. Eight patients had repeat transcranial surgery for a functional indication. Heterozygosity for the FGFR3 Pro250Arg mutation, present in 29 patients in the cohort, was the only factor found to have a significant association (P=0.048) with the transcranial reoperation rate. Six patients (20.7%) with the mutation underwent reoperation on the basis of raised intracranial pressure, as compared with two patients (4.3%) without the mutation. This highlights the need for genetic analysis and long-term clinical follow-up in apparently "isolated" coronal synostosis.