Behavioural interactions between parents and their developing offspring were studied in 13 captive groups of Owl monkeys. The male parent plays an important role in carrying the offspring and in ensuring the development of its independence. Older siblings also carry infants, but this behaviour is infrequent and age or sex differences are not measurable. Patterns of parental behaviour in Owl monkeys are compared to those observed in other monogamous primates and their adaptive significance is discussed. Some experimental studies of clinging positions in infant Owl monkeys are also described. The newborn possesses some innate ability to cling in a distinctive ventro-lateral position upon the mother's body.