Immunology. The title of the article “An essential role for tyrosine kinase in the regulation of Bruton’s B-cell apoptosis” by J. Simon Anderson, Mark Teutsch, Zengjun Dong, and Henry H. Wortis, which appeared in number 20, October 1, 1996, of Proc. Natl. Acad. Sci. USA (93, 10966–10971), appeared incorrectly due to a printer’s error. The correct title is “An essential role for Bruton’s tyrosine kinase in the regulation of B-cell apoptosis.”