The frontal sinuses make an important contribution to normal forehead and glabellar contour. This study was designed to test our clinical impression that early fronto-orbital ("frontal bone") advancement could have an adverse effect on frontal sinus development and consequently on forehead aesthetics. A retrospective study was conducted on 11 patients who had undergone fronto-orbital advancement and also had a long period of follow-up at the Institute of Reconstructive Plastic Surgery at New York University. The longitudinal cephalometric data were compared with unoperated controls. With one exception, no patient who underwent bilateral fronto-orbital advancement developed a frontal sinus, and all such patients had a flattened brow contour when compared with unoperated patients, of whom 82 percent developed at least one frontal sinus. Of the three patients who underwent unilateral fronto-orbital advancement for plagiocephaly (flattened forehead), two developed a frontal sinus but only on the unoperated side and one developed bilateral frontal sinuses. The two patients with unilateral frontal sinus development had a particularly obvious deformity resulting from normal glabellar projection on the unoperated side and a flattened contour on the operated side. Fronto-orbital advancement affects forehead aesthetics and should be performed only in infant patients with moderate to severe deformities. patients with plagiocephaly whose deformity is sufficiently severe to warrant surgery should preferably undergo bilateral fronto-orbital advancement (by the technique described) rather than unilateral advancement in order to avoid the brow asymmetry that results from unilateral frontal sinus development.