A survey of twelve families with 2 or more cot deaths showed that in two families the deaths were completely unexplained; in three the babies had a probably familial developmental disorder; in two the care of the infants was seriously at fault and could have contributed to death; and in five filicide was probable. 3 of the mothers in the last group were psychologically ill. Detailed pathological and psychosocial investigations are needed in dealing with these deaths and in planning the care of future children.