Medical Sciences. In the article “Core binding factor β-smooth muscle myosin heavy chain chimeric protein involved in acute myeloid leukemia forms unusual nuclear rod-like structures in transformed NIH 3T3 cells” by Cisca Wijmenga, Paula E. Gregory, Amitav Hajra, Evelin Schröck, Thomas Ried, Roland Eils, P. Paul Liu, and Francis S. Collins, which appeared in number 4, February 20, 1996, of Proc. Natl. Acad. Sci. USA (93, 1630–1635), the authors request that the following be noted. “The basic conclusion of this paper, that the CBFβ-SMMHC chimeric protein forms nuclear rod-like structures in NIH 3T3 cells in which the protein is overexpressed, appears correct. However, the data shown in Figs. 3, 5, and 6, involving deletions of the chimeric protein, should be disregarded.”