Overgrowth presenting at birth requires blood glucose monitoring while a cause is sought. Among older children presenting with tall stature, common causes such as familial tall stature and simple obesity must be distinguished from rarer endocrine and genetic causes. Several genetic overgrowth syndromes carry increased risk of malignancy and regular screening is recommended. The use of high-dose oestrogen or testosterone in an attempt to limit final stature has limited efficacy and carries a significant risk of side effects. Endocrine and genetic assessment ought to be considered for cases of unexplained overgrowth.