The unusual actinomycetes strain No. E465-94 produced a complex of new glycopeptide antibiotics tallysomycin, which was separated by CM-Sephadex chromatography into two major components, A (C68H107N21O27S2) and B (C62H95N19O26S2). They were isolated first in a copper-chelated form and showed physico-chemical properties similar to those of the bleomycin-group of antibiotics. Tallysomycin exhibited broad antibacterial and antifungal activity, and was highly active in vivo against bacterial infections in mice. Tallysomycins A and B demonstrated potent activity in the prophage induction of lysogenic bacteria.