Physiology. In the article “Role of leptin in hypothalamic–pituitary function,” by W. H. Yu, M. Kimura, A. Walczewska, S. Karanth, and S. M. McCann, which appeared in number 3, February 4, 1997, of Proc. Natl. Acad. Sci. USA (94, 1023–1028), the authors request that the following be noted. In the “Materials and Methods” section on page 1024, paragraph 3, line 9, the authors indicate that they used recombinant human leptin. In fact, they used recombinant murine leptin.