NEUROSCIENCE. For the article “T cell deficiency leads to cognitive dysfunction: Implications for therapeutic vaccination for schizophrenia and other psychiatric conditions,” by Jonathan Kipnis, Hagit Cohen, Michal Cardon, Yaniv Ziv, and Michal Schwartz, which appeared in issue 21, May 25, 2004, of Proc. Natl. Acad. Sci. USA (101, 8180-8185; first published May 12, 2004; 10.1073/pnas.0402268101), the authors note the following: “The SCID mice used in the reported results were not RAG1 and RAG2 knockout mice; they were mice of the BALB/cByJSmn-Prkdcscid/J SCID strain.” This error does not affect the conclusions of the article.