New anthracycline antibiotics, serirubicin (1) and 1-hydroxyserirubicin (2) have been found in the culture filtrate of Streptomyces cyaneus MG344-hF49 (FERM BP-314), which had been previously reported to produce ditrisarubicins A, B (3) and C (1). In the present paper, the production, isolation and characterization of anthracyclines 1 and 2 are reported.