Neurobiology. In the article “On the spurious endoproteolytic processing of the presenilin proteins in cultured cells and tissues” by Nazneen N. Dewji, Chau Do, and S. J. Singer, which appeared in number 25, December 9, 1997, of Proc. Natl. Acad. Sci. USA (94, 14031–14036), the following correction should be noted. Lane 11 of Fig. 1A has been replaced. The revised Fig. 1A is printed below. This correction does not change the paper in any other way; in particular, the legend to Fig. 1 remains the same.