1. From the Cancer Prevention and Clinical Statistics Programs, Fred Hutchinson Cancer Research Center, Seattle, WA; Emory University, Atlanta, GA; St Jude Children's Research Hospital, Memphis; Vanderbilt University Medical Center, Nashville, TN; The University of Texas M. D. Anderson Cancer Center, Houston, TX; University of Minnesota Medical School, Minneapolis, MN; International Epidemiology Institute, Rockville, MD; and the University of Alberta, Edmonton, Alberta, Canada.