This SYNDROME was first described almost 40 years ago by Rubinstein and Taybi in seven children with broad thumbs and toes, facial abnormalities (beaked nose, heavy eyebrows, long eyelashes, hypoplastic maxilla, and a narrow, high arched palate), joint laxity, hirsutism, microcephaly, and mental retardation. By 1996, more than 600 patients with this SYNDROME had been reported. The majority of cases are sporadic. In 25% of the cases, submicroscopic deletions in, and chromosomal study is normal. In 12 16P 13.3 is identified. Mutations have recently been identified in non- deleted RTS patients. One case is a 6- year- old girl that was presented to us due to a speech delay. In physical examination, there are microcephaly, hypoplastic maxilla, high arched palate, talon cusps in teeth, beaked nose, a thin upper lip, heavy eyebrows, long eyelashes, joint (especially elbow) laxity, broad and angulated thumbs with flat nails, hirsutism, a stiff gait, and mental, motor, social and language retardation. Laboratory studies, including a brain C.T. scan, EEG, metabolic and chromosomal studies, and routine tests, were normal.