This manuscript was reviewed by the Publications Committee of the NIMH Collaborative Program on the Psychobiology of Depression and has its endorsement. This study was conducted with the participation of the following investigators: W. Coryell, M.D. (Co-Chairperson, Iowa City); P.W. Lavori, Ph.D., M.T. Shea, Ph.D. (Providence, R.I.); J. Fawcett, M.D., W.A. Scheftner, M.D. (Chicago); J. Haley (Iowa City); J. Loth, M.S.W. (New York); J. Rice, Ph.D., and T. Reich, M.D. (St. Louis). Other contributors included N.C. Andreasen, M.D., Ph.D., P.J. Clayton, M.D., J. Croughan, M.D., G. L. Klerman, M.D. (deceased), R.M. Hirschfeld, M.D., M.M. Katz, Ph.D., E. Robins, M.D., R.W. Shapiro, M.D., R.L. Spitzer, M.D., G. Winokur, M.D. (deceased), and M.A. Young, Ph.D.