Evolution. In the article “Accurate reconstruction of a known HIV-1 transmission history by phylogenetic tree analysis” by Thomas Leitner, David Escanilla, Christer Franzén, Mathias Uhlén, and Jan Albert, which appeared in number 20, October 1, 1996, of Proc. Natl. Acad. Sci. USA (93, 10864–10869), the authors request that the following correction be noted. When the epidemiological data for this investigation were collected, the study subjects were assigned codes to protect their identity. Unfortunately, one individual was not assigned the correct code, thus p11 should be p10. The phylogeny that describes the known transmission history has been corrected and should read ((((p8.822, p8.159),(p10.113, p10.9939)), p9.256),(p7.6760,((p5.317, p6.6767),((p2.135,(p3.529, p3.105)),(p1.719, p1.136))))). The GenBank sequence files (U68496–U68521) also have been updated with the corrected labels and the correct topology. Furthermore, all results presented in the paper have been reevaluated and were found to be virtually identical to the published results. Thus, the published findings and conclusions remain unchanged. A detailed account for the reanalyses can be obtained from the authors. Dr. Leitner can be reached at his current address: Theoretical Biology and Biophysics, Group T-10, Mail Stop K710, Los Alamos National Laboratory, Los Alamos, NM 87545. e-mail: tkl@t10.lanl.gov.