1. Departments of Urology, Biostatistics and Epidemiology, Cleveland Clinic Foundation, Cleveland, Ohio and Departments of Urology, Mayo Clinic, Rochester, Minnesota, University of Iowa, Iowa City, Iowa, University of Southern California Medical Center and University of California at Los Angeles School of Medicine, Los Angeles, California, Brigham and Women's Hospital, Boston, Massachusetts, James Buchanan Brady Urological Institute, Baltimore, Maryland and University of Washington, Seattle, Washington