MEDICAL SCIENCES. For the article “Comparative PRKAR1A genotype–phenotype analyses in humans with Carney complex and prkar1a haploinsufficient mice,” by Mark Veugelers, David Wilkes, Kimberly Burton, Deborah A. McDermott, Yan Song, Marsha M. Goldstein, Krista La Perle, Carl J. Vaughan, Art O'Hagan, Kenneth R. Bennett, Beat J. Meyer, Eric Legius, Mervi Karttunen, Reijo Norio, Helena Kaariainen, Michael Lavyne, Jean-Philippe Neau, Gert Richter, Kaan Kirali, Alan Farnsworth, Karen Stapleton, Peter Morelli, Yoshinori Takanashi, John-Steven Bamforth, Franz Eitelberger, Irene Noszian, Waldimiro Manfroi, James Powers, Yoshihiko Mochizuki, Tsuneo Imai, Gary T. C. Ko, Deborah A. Driscoll, Elizabeth Goldmuntz, Jay M. Edelberg, Amanda Collins, Diana Eccles, Alan D. Irvine, G. Stanley McKnight, and Craig T. Basson, which appeared in issue 39, September 28, 2004, of Proc. Natl. Acad. Sci. USA (101, 14222–14227; first published September 15, 2004; 10.1073/pnas.0405535101), the authors note that the abbreviation rMSSD has been incorrectly defined on page 14225 as “root mean square of successful differences” and should have read “root mean square of successive differences.”