Medical Sciences. In the article “Hodgkin and Reed-Sternberg cells in lymphocyte predominant Hodgkin disease represent clonal populations of germinal center-derived tumor B cells,” by Andreas Braeuninger, Ralf Küppers, John G. Strickler, Hans-Heinrich Wacker, Klaus Rajewsky, and Martin-Leo Hansmann, which appeared in number 17, August 19, 1997, of Proc. Natl. Acad. Sci. USA (94, 9337–9342), the following corrections should be noted. (i) On page 9338, left column, the correct primer concentration in the first round of amplification is 0.04 μM. In the second round of amplification, the primer concentration for each V_H leader primer is 0.125 μM, and 0.031 μM for the nested J_H primer mix. In the first round of amplification 1.25 units Expand enzyme mix is used. (ii) The VH leader primers cited in ref. 27 were modified for the single cell analysis. The sequences are as follows: VH1, 5′-CTCACCATGGACTGGACCTGGAG-3′; VH2, 5′-TGCTCCAC(A/G)CTCCTGCT(G/A)CTGA-3′; VH3, 5′-ACCATGGAGTTTGGGCTGAGCTG-3′; VH3.2, 5′-ACCATGGAACTGGGGCTCCGCTG-3′; VH4, 5′-CTCCTGGTGGCAGCTCCCAGAT-3′; VH5, 5′-ATCATGGGGTCAACCGCCATCCT-3′. (iii) The correct accession numbers for the Genbank database are Y13787–Y13791.