Five previously published and one novel case history of children who suffered extreme deprivation in early childhood are reviewed. Aspects of cognitive, emotional and social development are subject to critical appraisal and three main issues, central to theories about the origins of developmental disorders, are addressed. Firstly, what minimal experiences during childhood are sufficient and necessary for normal psychological development? Secondly, are there critical periods in development during which inadequate exposure to certain experiences has long-lasting or permanent sequelae? Thirdly, what minimal compensatory influences are necessary to alleviate psychological handicaps resulting from an adverse early environment?