Medical Sciences. In the article “Results of MDR-1 vector modification trial indicate that granulocyte/macrophage colony-forming unit cells do not contribute to posttransplant hematopoietic recovery following intensive systemic therapy,” which appeared in number 26, December 24, 1996, of Proc. Natl. Acad. Sci. USA (93, 15346–15351), the following correction should be noted. The authors wish to point out that Dr. Fu’s name was omitted from the author line. The correct listing for the author line is: E. G. Hanania, R. E. Giles, J. Kavanagh, S. Q. Fu, D. Ellerson, Z. Zu, T. Wang, Y. Su, A. Kudelka, Z. Rahman, F. Holmes, G. Hortobagyi, D. Claxton, C. Bachier, P. Thall, S. Cheng, J. Hester, J. M. Ostrove, R. E. Bird, A. Chang, M. Korbling, D. Seong, R. Cote, T. Holzmayer, E. Mechetner, S. Heimfeld, R. Berenson, B. Burtness, C. Edwards, B. Bast, M. Andreeff, R. Champlin, and A. B. Deisseroth.