The editors regret editing errors in the October Correspondence, "Anti-Gal antibodies—where's the beef?" (Nat. Biotechnol. 17, 938, 1999). In paragraph 3, regarding the putative anti-Gal reaction in vivo, citations were omitted from the last sentence: ". . .should be routinely detectable as complexes in vivo8,9 at baseline. . .". In paragraph 4, an incorrect antibody drug name was listed. The third sentence should begin: "Similarly for Synagis12 and ABX-IL8 (ref. 13). . ." Finally, the affiliation wrongly listed Harvard Medical School in Harvard, MA—it should be Boston, MA—and Dr. Junghans' email address is correctly: junghans@hms.harvard.edu.