In the article, “2-Methyl-3-Hydroxybutyryl-CoA Dehydrogenase (MHBD) Deficiency: An X-linked Inborn Error of Isoleucine Metabolism that May Mimic a Mitochondrial Disease,” by Celia Perez-Cerda, et al., appearing in Pediatric Research 58:488–491, 2005, two authors' names were left off. The list of authors should have included Celia Perez-Cerda, the first author, and Antonia Ribes, the last author. The editors regret the error.