36 volunteer Naval enlisted men underwent isolation for 48 hr.during a srudy of conditions of "relaxation." Each S spent 24 hr. alone in dark quiet sensory deprivation (SD) and 24 hr. in a control condition (C) providing a virtual stimulus cafeteria. The amount of time S listened to a boring stock market report during 1 hr. each day was used as an index of stimulation-seeking need. Significantly more listening occurred while Ss were in the S D than in the C condition. Stimulation-seeking results were compared with various pre-isolation predictor tests, criterion measures during isolation and with post-isolation reports of isolation symptomatology.In an attempt to bring some theoretical order co various facts that were being gathered during early "percepnial isolation" experiments, Hebb (1955) called upon the concept of homeostasis. It was assumed that there is an optimal level of stimulation desired (or required) by an individ~ial and that marked deviations from this level should prompt efforts to bring the system back into "balance." Thus, just as a person attempts to remove himself from high noise fields and other stimulus overload situations, so shoiild he attempt to correct or avoid experiences involving stimulus underload. "Sensory deprivation" and "perceptual deprivation" are underload examples. In the former, there is typically a severe reduction in the physical stimuli that are permitted to impinge upon S's receptors. In the latter, meaningful perceptions are grossly reduced by immersing S in a world of unchanging stimuli, e.g., constant white light and white noise. The notion that persons undergoing conditions such as these should experience considerable "stimulus hunger" is now common. The problems of uncovering proof for the existence of such a "need and in determining its relevance to various isolation phenomena are, all at the same time, interesting, challenging, and cornplicated. It is clear at this time that the answers are not simple, as a survey of research results will reveal. 'We gratefully acknowledge the sizable assistance rendered by many individuals without whom a project of this magnitude could never be undertaken. The following can be only a partial listing. The contributions of our permanent staff members, Eugene Johnson, 111, Estelle N . Kushner, Peter M. Edmondo, and Stephen L. Milstein, were of the highest order in all phases of the srudy. Their efforts were well augmented by the summertime services of