Lactoferrin 17-41 (Lactoferricin B) acetate, a peptide corresponding to residues 17-41 of bovine lactoferrin, has antimicrobial activity against a wide range of microorganisms, including Gram-positive and Gramnegative bacteria, viruses, protozoa, and fungi. Lactoferrin 17-41 acetate has antitumor activities.