Neurobiology. In the article “Investigating neural correlates of conscious perception by frequency-tagged neuromagnetic responses” by Giulio Tononi, Ramesh Srinivasan, D. Patrick Russell, and Gerald M. Edelman, which appeared in number 6, March 17, 1998, of Proc. Natl. Acad. Sci. USA (95, 3198–3203), the following correction should be noted. In the legend to Fig. 1 (p. 3200, lines 3–5 of the figure legend), the printed value for f2 (8.33 Hz) is incorrect and should be replaced by 9.50 Hz. The correction does not change the paper in any other way, and the legend to Fig. 1 is otherwise correct. In particular, the reference to Fig. 1 in the second paragraph of the Results section correctly states the values of the two frequency tags.