From the culture broth of Streptomyces nodosus MH190-16F3, four new antibiotics have been isolated, and named saquayamycins A, B, C and D. The compounds are glycosides of aquayamycin, and among aquayamycin-group antibiotics they are most closely related to P-1894B (vineomycin A1). All saquayamycins act on Gram-positive bacteria and inhibit the growth of adriamycin-sensitive and adriamycin-resistant P388 leukemia cells. In the course of our screening study for new antitumor antibiotics, which are effective on both adriamycin-sensitive (P388/S) and adriamycin-resistant (P388/ADR) sublines of P388 leukemia, new aquayamycin-group antibiotics were isolated from the culture broth of a strain classified as Streptomyces nodosus MH190-16F3. All these antibiotics consisted of aquayamycin (an aglycone) and three sugar molecules, and we named them saquayamycins A (1), B (2), C (3) and D (4). This paper describes the isolation, physical properties, structure elucidation and biological activities of the new antibiotics.