The deleterious effects of separation and deprivation using children who were undergoing chemotherapy for childhood cancer was investigated. Extensive observational and physiological records were obtained on four children under five years of age during six weeks of treatment in a protected environment. In general, findings parallel those reported in the subhuman primate literature with the children's behavior following a descriptive sequence of agitation followed by behavioral depression. Results suggest that the seriousness of maternal separation for young children and the need to identify patterns of functional and dysfunctional behaviors have direct implications for intervention strategies. (Author)