Pharmacology. In the article “Systemic biosynthesis of prostacyclin by cyclooxygenase (COX)-2: The human pharmacology of a selective inhibitor of COX-2” by B. F. McAdam, F. Catella-Lawson, I. A. Mardini, S. Kapoor, J. A. Lawson, and G. A. FitzGerald, which appeared in number 1, January 5, 1999, of Proc. Natl. Acad. Sci. USA (96, 272–277), the authors inadvertently omitted the acknowledgment of the support from the General Clinical Research Center where these studies were performed. The relevant grant is NIH-MO1RR 00040.