An in depth study on growth, bone age, cranial CT scans and plasma somatomedin activity (SM-act) was made of 22 children with Sotos syndrome. In addition to the known characteristics of the syndrome, thin and brittle nails were found in three adolescent patients. The mean body stature, expressed as standard deviation score, increased from 2.2-2.8 in the 1st year of life, followed by a fall to 2.0 in the 2nd year. Thereafter the SDS increased slowly to values of 3.0 at 10 years of age. At least two subjects have reached an exceptionally tall final stature. After the age of 2 years, delta SDS/year remained very stable (-0.1-0.2), concurring with growth velocities in the upper normal range. Bone age was advanced in all patients. Cranial CT scans showed ventricular widening, mid-line cava and Sylvian anomalies in nine, six, and three patients respectively. SM-act dropped from high or normal values in the 1st year, to below normal from 1-5 years, and returned thereafter to the lower half of normal or below the normal range.