In the article, “Subunit Interaction Determines IKs Participation in Cardiac Repolarization and Repolarization Reserve,” by Silva and Rudy, which appeared in the September 6, 2005, issue of the journal (Circulation. 2005;112:1384–1391), Figure 1 contains typographical errors; the rate constants are not consistent with those used in the simulations. The revised figure below reflects the rate constants used in the code. None of the results or conclusions in the article are affected. The authors regret the error.