In the article “A Unique Role of RGS9-2 in the Striatum as a Positive or Negative Regulator of Opiate Analgesia,” by Kassi Psigfogeorgou, Dimitra Terzi, Maria Martha Papachatzaki, Artemis Varidaki, Deveroux Ferguson, Stephen J. Gold, and Venetia Zachariou, which appeared on pages 5617–5624 of the April 13, 2011 issue, the authors regret that one author's name was spelled incorrectly: “Kassi Psigfogeorgou” should have read “Kassi Psifogeorgou.”