MICROBIOLOGY. For the article “Attenuation of virulence in Mycobacterium tuberculosis expressing a constitutively active iron repressor” by Yukari C. Manabe, Beatrice J. Saviola, Li Sun, John R. Murphy, and William R. Bishai, which appeared in number 22, October 26, 1999, of Proc. Natl. Acad. Sci. USA (96, 12844–12848), the authors note the following correction. In Table 2, the IB-1 accession number should read Rv0757. The IB-2 accession number should read Rv0761c. The IB-4 gene name is rrs, the accession number should read MTB00019, and the description should read: “A portion of the 16S ribosomal RNA.”