Neurobiology. In the article “Functional activation in motor cortex reflects the direction and the degree of handedness” by Paul Dassonville, Xiao-Hong Zhu, Kâmil Uǧurbil, Seong-Gi Kim, and James Ashe, which appeared in number 25, December 9, 1997, of Proc. Natl. Acad. Sci. USA (94, 14015–14018), the following correction should be noted. On page 14017, the legend of Fig. 3 should end with the following sentence: “Other regions of cortical activation did not show a relationship between laterality and the extent of handedness, and have therefore been masked in the figure for clarity.” Also, in the acknowledgments, an additional source of support (National Institutes of Health National Research Resource Grant P41 RR08079) was inadvertently omitted.