We report two related Thai children having a new syndrome of microcephalic osteodysplastic primordial dwarfism (MOPD). The findings which classify them as having MOPD include IUGR, microcephaly, prominent nose and nasal bridge, small pinnae, short stature, cone-shaped and ivory-epiphyses, delayed bone age, slender long bones, and abnormal pelvis. The findings that distinguish them as having newly recognized syndrome consist of severe microdontia, malformed teeth, single-rooted or rootless teeth, severely hypoplastic alveolar bone, café au lait spots, acanthosis nigricans, and areas of hypo-and hyperpigmented skin. The reported patients appear to have the same condition as the family reported by Kantaputra [2002: Am J Med Genet 111:420-428]. This article contains supplementary material, which may be viewed at the American Journal of Medical Genetics website at http://www. interscience.wiley.com/ jpages/0148-7299/suppmat/index.html. © 2004 Wiley-Liss, Inc.