In this meta-analysis of 75 studies on more than 3,888 children in 19 different countries, the intellectual development of children living in children's homes (orphanages) was compared with that of children living with their (foster) families. Children growing up in children's homes showed lower IQ's than did children growing up in a family (trimmed d = 0.74). The age at placement in the children's home, the age of the child at the time of assessment, and the developmental level of the country of residence were associated with the size of the delays. Children growing up in children's homes show a substantial lower level of IQ (average IQ of 84) than their peers reared in (foster) families (average IQ of 104), and the difference amounted to 20 IQ points. More research is needed to detect the causes of the large IQ delays and to test ways of improving the intellectual development of millions of children in orphanages around the world.