The hypothesis that separation in early life predisposes one to later psychopathology was tested using two groups of rhesus monkeys of similar age. The experimental group had undergone the stress of early life separation and confinement in a vertical chamber. The experimental animals responded to separation and reunion with increased self-mouthing, self-clasping, huddling, and rocking. The control group responded to separation with increased locomotion and responded to reunion with increased contact clinging and proximity behaviors. The implications of these findings are discussed.