Sotos syndrome (cerebral gigantism) is characterized by macrocephaly, global developmental delay, characteristic facial dysmorphology, and a markedly advanced bone age. The purpose of this study was to describe the prevalence of Sotos syndrome in a consecutive series of patients with global developmental delay, which might modify our laboratory evaluation approach to this particular clinical situation. For a 10-year inclusive interval, the case records of all consecutive patients referred for global developmental delay in a single pediatric neurology practice were reviewed. Patients with macrocephaly were defined by an age- and gender-adjusted head circumference greater than or equal to the 98th percentile. Possible clinical factors associated with eventual diagnosis of Sotos syndrome in this group of macrocephalic children were tested with a two-tailed Fisher exact test. Of 261 children with global developmental delay, 18 (7%) had documented macrocephaly. Of these 18 children, 3 (17%) had an advanced bone age and were diagnosed with Sotos syndrome. In patients with global developmental delay and concomitant macrocephaly, Sotos syndrome is not uncommon. Assessment of bone age is a simple screening test for diagnosis of this entity and should be undertaken routinely in children with macrocephaly and global developmental delay even in the absence of other distinctive syndromic clinical features.