✓ The effect of timing of the surgical release of prematurely immobilized coronal sutures was studied in rabbits. At 9 days of age, the coronal suture was mechanically immobilized by the application of methyl cyanoacrylate adhesive. These animals and a control group then received metallic implants on each side of the suture to monitor growth. At 30, 60, or 90 days after suture immobilization, separate groups of animals underwent a linear suturectomy to release the restriction. In animals in which the suture was not released, growth at the coronal suture was significantly restricted and resulted in severe deformities in the neurocranium. The benefits derived from surgical release were time-dependent. Suturectomy at 30 days of age resulted within 60 days in achievement of 100% of the growth in sham-treated controls. In contrast, delayed surgery at 60 or 90 days of age resulted in achievement of only 38% and 17% of normal growth, respectively. Angular measurements of the vault and base of the cranium showed a similar graded response toward normality, with the greatest correction occurring with the earliest operation. These results support the clinical impression that early surgical correction of craniosynostosis results in superior cosmetic appearance. A further implication of this work is that abnormality at a single suture strongly influences the development of other areas in the craniofacial complex.