Medical Sciences. In the article “Expression of the fructose transporter GLUT5 in human breast cancer” by S. Pilar Zamora-León, David W. Golde, Ilona I. Concha, Coralia I. Rivas, Fernando Delgado-López, José Baselga, Francisco Nualart, and Juan Carlos Vera, which appeared in number 5, March 5, 1996, of Proc. Natl. Acad. Sci. USA (93, 1847–1852), the authors request that the following be noted. “Our statement regarding the absence of GLUT5 immunoreactivity in normal breast tissue needs to be revised. Subsequent analysis done with more sensitive methodology revealed GLUT5 immunoreactivity in some normal breast ductal epithelium. Our conclusion regarding the expression of GLUT5 in human breast as a specific manifestation of the neoplastic state is therefore premature.”