Immunology. In the article “Modifying the sequence of an immunoglobulin V-gene alters the resulting pattern of hypermutation,” by Beatriz Goyenechea and César Milstein, which appeared in number 24, November 26, 1996, of Proc. Natl. Acad. Sci. USA (93, 13979–13984), the following revision should be noted: The formula at the bottom of the first column of page 13980 was misprinted. The correct formula is: