Task ENDORSE began in 1956 at a time when interest in the effects of sensory deprivation was high. The coercive aspects of confinement of prisoners of war in a world of drastically limited sensory experience and social isolation led to interest in the research problem by the Assistant Chief of Staff, Intelligence, Department of the Army. At the same time, since the fundamental problem is that of the effects of monotonous surroundings, findings could be expected to have broad implications for other areas of military interest as well. The research task proposed at that time was subject to close scrutiny because of the concern that the experimental conditions might have harmful effects on subjects, and because the laboratory approach it represented was unique within the usual scope of HumRRO research activities. Various possibilities for conducting such an investigation were explored, seeking profitable means for studying this seemingly potent environmental condition, and permission was obtained to tackle the first problem--the safety aspect. A pilot study, using staff experimenters themselves as subjects and utilizing crudely constructed devices and methods for limiting sensory experience, demonstrated the feasibility of the project, at least with regard to safety from severe physical and mental hazards to the subjects. After the pilot study, considerable time was devoted to extensive planning as to the type of laboratory needed to conduct the research, and to cautious study of the implications of establishing such a laboratory and the research approach implied.