Biophysics. In the article “Characterization of lipid bilayer phases by confocal microscopy and fluorescence correlation spectroscopy” by Jonas Korlach, Petra Schwille, Watt W. Webb, and Gerald W. Feigenson, which appeared in number 15, July 20, 1999, of Proc. Natl. Acad. Sci. USA (96, 8461–8466), due to a printer’s error, the following changes should be noted. The first sentence of the legend to Fig. 2 should read: Diffusion properties in laterally ordered and fluid phases in the absence of cholesterol, corresponding to Figs. 1, 2A, 2C, and 2E. Also, the legend to Fig. 4 should read: FCS autocorrelation curves corresponding to the cholesterol compositions shown in Fig. 1, 3, at constant DLPC/DPPC = 0.50/0.50.