The National Institute of Mental Health Collaborative Program on the Psychobiology of Depression—Clinical Studies was conducted with the participation of the following investigators: M. B. Keller, MD (Chairperson, Providence, RI); W. Coryell, MD (Co-chairperson, Iowa City, Iowa); T. I. Mueller, MD, D. Solomon, MD (Providence); J. Fawcett, MD, W. A. Scheftner, MD (Chicago, Ill); W. Coryell, MD, J. Haley (Iowa City); J. Endicott, PhD, A. C. Leon, PhD, J. Loth, MSW (New York, NY); J. Rice, PhD, T. Reich, MD (St Louis, Mo). Other contributors include H. S. Akiskal, MD, N. C. Andreasen, MD, PhD, P. J. Clayton, MD, J. Croughan, MD, R. M. A. Hirschfeld, MD, L. Judd, MD, M. M. Katz, PhD, P. W. Lavori, PhD, J. D. Maser, PhD, M. T. Shea, PhD, R. L. Spitzer, MD, M. A. Young, PhD. Deceased: G. L. Klerman, MD, E. Robins, MD, R. W. Shapiro, MD, G. Winokur, MD.