Mechanism of Psoralen Photosensitization and In Vivo Biological Action Spectrum of 8-Methoxypsoralen11From the Research Laboratories of the Department of Dermatology of the Harvard Medical School at the Massachusetts General Hospital, Boston 14, Massachusetts.This work was supported by Grant #CY 5003 (C-1) from the National Institutes of Health, United States Public Health Service. The mono-chromator used was purchased with funds generously donated by Dr. and Mrs. John Alden of San Francisco.Presented at the Twenty-second Annual Meeting of The Society for Investigative Dermatology, Inc., New York, N. Y., June 29, 1961.