The chapters gathered together here serve as the selected proceedings of the 4th International Congress on Restricted Environmental Stimulation (REST) held in Washington, DC, in 1990. The congress was sponsored by the International REST Investigators Society (IRIS). Arreed Barabasz, President of IRIS, and his wife Marianne Barabasz, edited the volume. They have been very active researchers in this area, and authored or coauthored 11 of the 30 chapters. Altogether there are 34 different authors and coauthors represented.