The authors of “Changes in the Distribution of Extracellular Matrix Components Accompany Early Morphogenetic Events of Mammalian Cortical Development” (A.M. Sheppard. S.K. Hamilton, and A.L. Pearlman, J Neurosci 11:3928–3942, 1991) would like to correct an error in calculating the calibration bars in three of the figures. The correct calibrations are: Figure 2, 50 ¨m; Figure 6,50 ¨m; Figure 7, 100 ¨m.