A strain of Streptoverticillium cinnamoneum produced a peptide antibiotic named lanthiopeptin, which contained four unusual amino acids, erythro-beta-hydroxyaspartic acid, mesolanthionine, threo-beta-methyllanthionine and lysinoalanine. Lanthiopeptin showed antiviral activity against herpes simplex virus type 1 KOS strain infection in Vero cells by cytopathic effect reduction assay. The structure of lanthiopeptin is similar to that of ancovenin.