Mandibulo-facial dysostosis largely involves structures derived from the first branchial arch, groove, and pouch. The term, Treacher Collins syndrome, has been widely recognized as the condition which was indicated by E. Treacher Collins in 1900. Franceschetti and co-workers in 1944 published an extensive review of this syndrome and named it mandibulo-facial dysostosis. We encountered on May 17, 1968, a 46-year-old female with the right palpebral fissure slanting downward laterally (antimongoloid), microtia, hypoplasia of malar bone, zygomatic arch and mandibula on the right side, defect of muscular process and recession of the chin. Our case seems to belong to the unilateral form of mandibulo-facial dysostosis (Treacher Collins syndrome). This case was not discriminated from Goldenhar's syndrome.