We have obtained serial measurements on 180 patients with clinically confirmed Brachmann-de Lange syndrome (BDLS) in order to derive standard growth curves. The patients were evaluated in our genetics department and through meetings of the Cornelia de Lange Syndrome Foundation, a support group for families of affected individuals. The data were obtained from the records of pediatricians, other physicians, schools and parents, as well as from personal examination on each of these patients at least once, often periodically. The growth curves include height, weight and head circumference measurements from birth through adulthood. Prenatal growth and birth weights are below the 5th centile in most (68%) cases, with an average birth weight of 2,277 g. Growth persists below the normal curves in most of the patients throughout life. Height velocity is equal to the normal range but there is slower pubertal growth. Weight velocity is below the normal range throughout life until late adolescence. Average head circumference remains below the second centile. Thin body habitus coupled with slow growth and proportionate small stature is a manifestation of the syndrome, but is commonly mistaken for failure to thrive.